I'm also wondering about question no 1, ran into this situation yesterday, and didn't which one get to resolved first, is it Stretchy or Psychic Probe?
Meanwhile I found the answer.
There is no defined order.
If someone wants to play one of the cards - then he is allowed.
After playing the card any other player is also allowed to play any card that is still available.
So if player A wants to finish playing cards, but player B decides to play a card now, then player A is allowed to play a card again.