That is exactly what the OP did.  However he then imported that private key into the QT client and sent funds from it.

The larger issue is that one would either treat a wallet file as a complete unit (i.e. forget about individual keys) and treat the wallet as a single object which needs to be be backed up in its entirety OR use individual private keys in systems like offline paper wallets.

Anyone mixing both systems without understanding how it works under the hood is running the risk of losing funds.

I don't feel as sorry for them as I do the younger generation.   People who have lived their entire lives under a lie of unfunded entitlements aren't suddenly at age 60, 70, 85 going to say "oh well guess I need to get back to work it is the fair thing to do".  No they are going to use their considerable power as a voting block to ensure they keep as much of what was promised.  The consequences to the overall economy, the future of the country, and the quality of the life for the next generation be damned.

No it would be a double spend.  It would be a race to see which ones ends up in the block at which point the other transaction using the same inputs would be rejected by the network as a double spend. 

It doesn't matter if
a) both tx are signed by you with same private key
b) both tx are signed by you with different private keys (which produce the same public address)
c) the two tx are signed by different parties using the same private key (i.e. a stolen wallet and race to spend funds)
d) the two tx are signed by different parties with different private keys (i.e. a nearly 0% chance public address collision)

In all four outcomes both tx are valid, only one will end up in a block and that will invalidate the other tx as a double spend.

Same as any other software.  For example how can you ensure TOR really keeps your activities anonymous and doesn't just pretend to and then broadcast everything in plain text directly to the destination?  How can you ensure your encryption tool is really using AES as it advertises and not some backdoored government code which can be trivially bypassed by the state?

In any (open source) project you can:
a) write the code yourself.
b) validate the existing code yourself.
c) pay someone to validate the code.
d) trust the community of people (consisting of a,b,c above) to sound the alarm if software is released which is flawed (either accidentally or maliciously).

Actually it is not "legal" (recognized is probably a better word) to form a new nation anywhere in the world, at least not one recognized by any current nation.  The "nation" club is a members only club.  Even if there is some undiscovered land (unlikely since the development of global sat mapping) as soon as it is discovered it becomes part of the closest nation.  If a new landmass was built (i.e. massive scale terraforming) it likewise would become part of the closest nation.  The club sometimes expands when existing nations are split (usually due to conflict) but that is it.

Bitcoin is a distributed consensus system.  Every node (regardless of they are a miner or not) validates transactions, and blocks against certain rules.  It is this set of rules which "make" Bitcoin.  One of the rules concerns the amount of the mining subsidy.  It began at 50 BTC per block and is reduced by half every 210,000 blocks.  If a miner was to not reduce the subsidy (or increase it, or violate any other protocol rule) the block would be rejected by all other nodes as invalid.  Since miners only get "paid" when others build upon their block, other good miners will also reject that block and continue to build on the longest "legit" chain.

It is important to note even a majority (51%) or super majority of miners can't change this behavior as blocks are validated not just by miners but by all nodes.  It is unlikely for this reason that the core protocol rules will ever be changed.  Any such change would result in an incompatible fork of the Bitcoin project and the "original" would always exist.

No it doesn't need to be open, no there is no time limit (the particular client doesn't matter).  If you have been offline your client will need to update your local copy of the blockchain to be "current" and that may take some time if you have been offline for a while.  Your client needs a current copy of the blockchain in order to "see" coins which have been sent to you.  The client needs to "see" the coins in the block chain in order to update your wallet balance and create the transaction which allows you spend them.  

If you want the more complete answer.  Nobody ever sends Bitcoins TO YOU.  When someone "spends" Bitcoins they announce to the entire  network that change in ownership has occurred.  The network will validate and permanently store that change in ownership until such time as you announce another change in ownership.  Your wallet contains the private keys which ensure you and only you can do that.  If you never come online and spend those coins they will always exist in the blockchain and will never be spent.

Once an output is spent it can't be respent.  The network would see a second attempt to spend it no different than any other failed double spend.  If more funds are sent to this double private key address it would be a race on which party is able to make a transaction and get it included in a block first.  For all intents and purposes it would be no different than an attacker stealing your private key.  In terms of ability to spend (or not because funds are already spent) the network would see signatures from either party as having equal validity.

I would point out the odds of this happening are so astonishingly small as to essentially be 0%.  I don't mean win the lottery small (1 in 1.75E8 for US Powerball jackpot), it would be more like the exact same number sequence is the winning number for five sequential Powerball lottery drawings.

While with probabilities we can never say the odds are zero honestly this is close enough to zero because humans have a finite lifespan and are continually exposed to other risk factors which have a much greater probability of occurring.  To put it into perspective the, risks such as being murdered (1 in 18,000), dying from the elements, exposure, natural disaster (1 in 225,000), getting struck by lightning (1 in 775,000 per year), getting killed by SARS (1 in 1 mil for US residents during the last outbreak), being struck by a falling meteorite (1 in 1.8 million), getting killed by a shark (1 in 11.5 million per year) or being killed in a car accident (1 in 65 million per mile driven).

And the grand finale....  The odds of an asteroid strike of sufficient magnitude to cause an extinction level event is estimated at roughly 1 in 100 million per year.  That is roughly 1 in 36.5 billion per day,  1 in 876 million per hour, or 1 in 52 trillion per minute.      So the odds that the human race was wiped off the planet earth just during the time you were reading this post is roughly was 27,806,347,742,216,600,000,000,000,000,000,000x MORE likely than the odds of a random collision in a 160 bit space.

It is called a change address.  You can't spend part of an output.  So if you have an output worth 10 BTC and want to send 6 BTC the transaction has 6 BTC sent to your destination and another 4 BTC sent back to a change address.  Why a new address?  To preserve anonymity.  If the change address was always an existing address it would be trivial to track transactions.

Still your right if you don't know what you are doing..... don't frak around with private keys and make frequent backups.  Honestly the point of a cold wallet is to keep it as an offline backup, not to import it, and play around periodically.  You gain nothing and run the risk of doing something silly.

For sron to become rich without any work. 

I think you fail to realize that bitpay already removes 100% of currency risk.  Client can request payment amount in dollars and Bitpay will display payment amount in BTC to customers.  Regardless client gets the amount requested in dollars.

It seems you reinvesting the wheel and looking for others to take the risk of doing so.  I don't see such a poorly detailed plan getting funding.

When reps for a company are advising people to DO A CHARGEBACK you have to be an idiot to not RUN (not walk, RUN) for the exit.  There are chargeback fees of $25 to $50 on top of the cost of the refund.   It never makes sense for a company to request chargebacks over just issuing a refund.  Too many chargebacks means the comapny will lose their merchant account and likely see their reserve frozen for 180 days.  That is something that benefits nobody.

So a company NEVER asks customers to do a chargeback.  Ever.  For any reason.  The fact that anyone in the company is making that request should scare the crap out of any customer soon to be unsecured creditor of an insolvent company.

The miner program doesn't contribute that much of a difference.  With GPU mining it is important to make a distinction between the mining client (minimal impact on performance) and the OpenCL kernel.  The days of 2% gains in the OpenCL kernel are long gone.   The code has been highly optimized and IIRC the most recent major change was something on the order of 0.1% performance increase.  The client itself has never been the performance bottleneck. 

With ASICs (and FPGA) the OpenCL kernel is replaced by the chip itself.  The client is just about management and reporting.   Further I would point out the OP isn't claiming any type of performance increase.

Write a message in the GPG client.  Encrypt.  Copy and paste the encrypted contents into the body of an email.

Well you not knowing isn't the same thing as "not true".  It is true.  There are some retailers which allow purchase of MP by debit card.  Period.  That is a fact.  The fact that you didn't know of any doesn't change the fact.

Good to hear you pay cash and have receipts now if you will stop spreading misinformation maybe you will get some transactions.

Bitpay supports multiple shopping carts.  Just use a shopping cart provider which supports your needs. 

Not true some locations allow purchase by debit card and PINs can be brute forced.  So do you have receipts?  Or are there re-traded scammer garbage likely to get someone's account frozen?

PGP isn't email.  You send email using your email client. GPG just creates encrypted messages.  You can email them but you can also send them as a private message, transfer them by dropbox, hand them to the recipient on a usb drive, or even print them out.   GPG just encrypts messages, you can deliver them however you like.   To use an analogy your quesiton would be like asking how can you use winzip to email files.  Winzip is used to compress files and then you can send them however you like.

To encrypt a message that you can email there are multiple options but here is the simplest one (since you already have GPG4Win installed).

To create an encrypted message
Start GPA (In Windows Start > GPG4WIN > GPA)
Click on [Clipboard]
Write your message.
Click on [Encrypt]
Select the key of the recipeint (you can select yours as a test).
The clipboard will change to encrypted version of your message.
Copy the entire contents of the clipboard (entire mean entire include the BEGIN and END lines).
Open your favorite email program or webapp (gmail, etc).
Paste the encrypted message into the body of the email.
Send the email like normal.



To decrypt a message
Copy the entire encrypted message (entire means entire include the BEGIN and END lines).
Open GPA (Start > GPG4Win > GPA)
Click [Clipboard]]
Paste the encrypted message.
Click [Decrypt]
Enter your private key passphrase when prompted.
The clipboard will change to the decrypted message.

For testing you can encrypt a message to yourself, email it to yourself, then copy it back to GPA using the two sets of instructions above.

I recommend you also try installing Cryptophane (an alternative GPG "client").  

Well there probably is no economic incentive to do so.  People value PPC because they have some.  If you remine the chain back from the genesis block it is unlikely people will be lining up to buy "their" coins from you.  You could cause a lot of chaos, you could bring the chain to a standstill (the "Luke" attack - mine nothing but empty blocks and reject all other competitor blocks), you could rewrite history (given the token amount of "lifetime" hashes in the blockchain, but it is unlikely it would be very profitable.

Ok say 3 weeks from now after difficulty has increased twice.  The larger problem is the low hashrates of a TRC, PPC, and other SHA-256 based chains makes them highly susceptible to 51% attacks if for no other reason than LOLZ.  Eventually someone either trough true malice or mere curiosity is going to turn their attention towards an alt-chain.