Your question is unclear. Are you asking how the merchant knows that he has been paid? If so, it does it the exact same way that every wallet does. It connects to a node (or is a node) and is notified when the node learns of a transaction which spends to the addresses it is watching for.

I don't know. Blockchain.info has a lot of problems in general.

It depends on the service. Since addresses don't expire, you can still send to the same address. It's on the service to know that you attempted to bump the fee. If your transaction confirms but the service isn't recognizing it, then contact their support because that is on their end.

It will fix your problem. Rescanning should not take too long, but it does take a while since it has to scan through the entire blockchain.

The minor versions do not come out on a fixed schedule. They come out when there are urgent bug fixes or when a soft fork is ready to begin deployment. The major releases come out every 6 months or so. The next major release (0.13) is coming out very soon. The first release candidate has already been released, with the official version scheduled for August 1st.

It will happen after 0.13, in 0.13.1, and probably 0.12.2 as well. The release of it is still TBD.

The amount of BTC being sent does not matter. What matters is the actual size of the transaction in bytes. If you send the same amount in two transactions but one has more inputs than the other (thus making it bigger), then it will require a higher fee. Also, the condition of the network is constantly changing, so what worked a month ago may not work now.

It is stuck probably because your fee is too low. According to https://bitcoinfees.21.co/ (which is known to be fairly accurate)

2800 satoshis is not enough.

Since you are using Bitcoin Core, you should just use the fee that Bitcoin Core recommends. If you choose the "Recommended" option and move the slider to "Fast", it will give you a fee that is usually enough to get the transaction confirmed in the next block.

To fix this, in Bitcoin Core, go to Help > Debug Window and then the Console tab. In the box at the bottom, type
Where <txid> is the txid of your stuck transaction (when copying from the transaction list, make sure you remove the -000 that Bitcoin Core appends to the txid). Then hit enter. This will enable you to respend the inputs that you used in your stuck transaction so you can send it again but with a higher fee.

Yes. Performing such an attack would require a lot of hardware. In order to have any probability of success, you would need to have greater than 50% of the hash rate. At the current network hashrate, that is incredibly expensive and pretty much impossible.

Theoretically yes, in practice, no.

In order to do that, you would need to be able to mine three blocks before the rest of the miners find the block for the third confirmation. Those three blocks would have to include the double spending transaction and be a small fork of the blockchain the began on the block before your first confirmation.

No, not necessarily. Blockchain.info has some strange node policies. Not all nodes will reject transaction with more than 250 inputs. AFAIK, it isn't even a standardness rule, so the transaction still can be confirmed.

Yes you can update from 0.93.3 to 0.94.1 without uninstalling anything. Just download 0.94.1 and install. Since 0.94.1 uses a different database than 0.93.3, you will be able to save a lot of space by deleting the old databases. Go to %appdata%/Armory and delete the folder there named "databases". Then run Armory again and it will rebuild them. The new database is much faster to rebuild, so it should be done in a few minutes.

There will usually be many people who are willing to exchange paypal or neteller for Bitcoin. However, in most cases, you need to be trusted because PayPal and Neteller are reversible. Also, you will usually end up paying a high premium due to the risk that the seller takes by exchanging Bitcoin for something reversible.

It is actually hard to hack a wallet. Never use a web wallet; many times those websites have poor security practices and end up being hacked and the Bitcoin stolen, or they run away with your Bitcoin, or the service is just plain bad (e.g. blockchain.info).

If you have a hot wallet (a wallet that is on a computer connected to an internet), make sure that you keep the wallet software up to date, keep your operating system up to date, have an antivirus software, and use different strong passwords for your computer and your wallet. Always encrypt your wallet.

If you have a cold wallet (a wallet on a computer not connected to the internet, recommended), make sure that the computer you have the cold wallet on is clean of any viruses, and that you plan on never connecting that computer to the internet ever again.

Also make periodic backups and keep them in a secure, offline place.

Use gitian builds. If you are using some derivative of Bitcoin Core, it should be possible to adapt gitian to be used with it.

I can't verify your script since I am not sure on the behavior of OP_IF. However, there are some things that I can point out.

No. It has to be in Little Endian, so swap the bytes. It should be 0x3a0940.

No you cannot remove them. OP_CSV does not return an OP_TRUE, it acts as either a OP_NOP or it terminates the script execution with an error. If it passes, then nothing happens and it needs to be removed from the stack with OP_DROP. If it fails, then the transaction fails and is rejected.

Edit: Figured it out. Besides for the endianness, it all looks good.

If you go to File > Settings and uncheck "Let Armory start Bitcoin-Core in the background" and then restart Bitcoin Core and Armory, it should fix the problem. Also, always use the latest software.

They are just trusting the company to not steal the private key or record it beforehand.

If you have junk lying around in your house that you don't want but may be valuable to someone else (e.g. old computers), you can sell them on this forum or other marketplaces that accept Bitcoin.

If you have some sort of desirable skill, you can offer a service for Bitcoin. For example, if you can program, you can offer a programming service. Or if you fluently speak multiple languages, you can offer a translation service. Or if you can edit videos, you can make a video editing service.

You should not try to get Bitcoin for free, it isn't worth the time nor will there be a big payout. Rather you should either buy Bitcoin with your fiat, or sell some sort of good or service and be paid in Bitcoin.

You put it in the wrong place. It belongs in C:\Users\USER\AppData\Roaming\Bitcoin. If there is no folder there after running Bitcoin Core, then you are using a custom data directory. If you don't know what it is, go to Help > Debug Window and click the button to open the debug.log file. Look for where it says your data directory is and then put the wallet.date file in that folder.

That means that you did not put the backup in the right place, or it is the wrong backup file since the file there was created today.

Find the cloakcoin data directory and then replace the wallet.dat file in there with your backup.

Make sure that you are copying the backup to the right place. Right click the wallet.dat file in the data directory and click on properties. Make sure that the "Created" field has a date that makes sense for that wallet to have been created (e.g. 2013).

If you have made any transactions between when that backup was made and when you imported it to Bitcoin Core, it is possible that the backup does not contain the private keys that control your Bitcoin. Since Bitcoin Core is not a deterministic wallet yet, you need to have made a backup of the wallet every 100 transactions.

Do you see any transaction history?

Find an address that you know should have been on that wallet. Then go to Help > Debug Window and click the Console tab. Then in the box at the bottom, type
where <address> is the address that you know should be on that wallet. This will give you the private key for that address. DO NOT SHARE IT WITH ANYONE. If you do get the private key, it should be in black text and begin with a "5", "K", or "L". If you get an error in red text, then that means the address is not in the wallet and you have the wrong wallet.

If you do have the wrong wallet, try copying the backup in again.

You should also try getting the wallet from the windows drive. Make a live CD or USB of another OS such as Ubuntu. Then boot from that on the windows pc and try to access the Windows hard drive. Then pull the wallet.dat file from there.

Buy a more recent hardware such as the Antminer S9, which provides ~12 Th/s. However your electricity costs are too high and you will be mining at a loss. I do not know of any more energy efficient hardware than the S9.