First rule of smart trading is NEVER invest all of your money in 1 coin, especially when you don't really know about this coin much. But if you already are invested big portion of your money then watch the charts, previous history, learn from the more experienced traders who is trading this particular coin for a long time and then you will decide what to do. Forget about your emotions now. Study on your mistakes and try to avoid them in the future.
No, the first rule of smart trader is manage your capital. As long as you can do it's well, you can trading anything, any type without any limit ... Why do the forex trader just traded USD-BTC but they still have a lot of profits from Bitcoin, because they can manage their capital and know their moves.
Yes, it is true. Recently, I also just trade USDT-BTC or USDT-Altcoin pair, but the profit not worse than the profit I earned through Bitcoin-Altcoin trading. The first skill to become a trader is management your capital, it is very important to become a real trader instead of gambler.