Tax questions regarding altcoins and forks

I am in the USA. I have some questions. I've been hesitant to sell any more bitcoins because it might push me into a higher tax brackets. However, with my altcoin trading, it may be irrelevant, depending on the answers to these questions:

1. If I trade an altcoin for bitcoin and make a profit in bitcoins, but never touch the US dollar (Sell) by the end of the tax year, are the profits taxed or not?
2. If I am taxed on the altcoin profits, and the the bitcoins that I traded with were a long term hold, are the altcoin profits taxed as a short term hold or a long term hold?
3. If I am taxed on the altcoin profits, what price basis is the tax - is it the price of bitcoin at the time that I closed the trades?

4. If bitcoin forks into bitcoin cash, etc, but I dont sell, am I taxed?
5. If I am taxed on the fork, and the the bitcoins that I had held were a long term hold, is the fork taxed as a short term hold or a long term hold?
6. If I am taxed on the fork, what price basis is the tax - is it the price of bitcoin at the time of the fork?

Thanks