I think those crypto currency will be used world wide.  It will contribute more in the future because of its great valve. It has more use and can be used easily

You can earn bitcoin using different  ways
1. joining on signature  campaign
2. By trading
3. By investing
4. On faucet
5. By gambling

I think paper money will definitely end someday and it would be replaced by different  online currency  like bitcoin and others which can be used like a paper money

Mining is a way using our computer  or any gadgets  to earn online
While trading is a way which you can buy and sell a pruduct

Its better to read more about bitcoin for you to understand more about posting into different  forums.
It is better because once you join into different  campaign  there is a rule to be followed about posting

For me its beter to have a wallet than paypal...  Like coins.ph it is more legit than paypal

You can increase your bitcoin by trading,  and by joining to different campaign

It is considered  post every time  you post or comment to different  forums like this
Every 14 days there is an update that counts your activities to check for it just refer to your profile 

We need virtial currencies  because it can be used worldwide.  It was easy to use , it can be used such us in paying bills specially in online transactions .

Yes it is and we need to take action on it.  Lots of green house  gases pollution are emitted on earth that cause in global warming..

Yes i think because btc now a days are very popular and many peaple used it some of them are billionaires