If I or one of my referalls sign up for a trial offer, but after the trial period I/they are dissatisfied and decide to cancel - does that mean I won't be able to get my prize?
no, the site credits if you try the trial, and as long as you stay a member for the time specified - for hosting is usually 1 month, all should be fine
one more question - what if you accepted and confirmed a trade but for some reason can't complete your side of the bargain, for example you can't get a green. Is there a way to cancel the trade without being penalized or something?
yeah, either you both request deletion or both indicate trade failed.
D you should let the other user know first
Contact the person you have the trade going with. If no greens or money have already been transfered, then you can both request the trade to be canceled.