Hello everyone
1- Where is the best place to Buy/Sell Bitcoin which has the most convenient methods to Buy/Sell and supports as much countries as possible?
Localbitcoins I think supports almost country and there are several payment methods you can use so it really is reliable.
2- Where are the best places to count on when looking for the BTC/USD rates?
Personally I look at preev rate. It's higher than the local rates. I don't know what others are using.
3- What is the best place to trade Bitcoin at?
Trade bitcoin to altcoin or trade bitcoin to fiat?
localbitcoin for fiat trading, paxful, bitfinex, bittrex for alts, c-cex poloniex.
4- Is it possible (anymore) for a Bitcoin payment to gets confirmed if it has no fees?
No. You need to send a transaction with enough fee to get confirmed.