Q2: I think the idea is that if BTC price is shooting up you want to sell your altcoins to be in BTC. But that is just a guess.
Good Luck!
So, the difficulty change/increase due to hash mining pointing to the coin. All this makes the question clear to me. Thank you.
Yes. A good way to think about it is like this:
There are 50 coins per block. There is one person mining, at 10 MH/s. The difficulty is now 10. He earns all 50 coins every block since he mines them all.
Another person starts mining at 10 MH/s. The difficulty is now 2x, or 20. Each person earns around 25 coins per block since, on average, each will get 1/2 of the blocks.