A: It can't be any problem if they don't raise it. Around here, no one is going to come after you if you use an idea they
gave you. If it's an idea not intended to help you (copying someone's story premise) that's a bit rough, rude, but again, unless someone from around here is going to make trouble, there is no trouble.
B: Unless they provided the idea as part of a contract to get credit or something... it's just the same as using a cliche line, telling a good joke, etc. Your repeating someone else's good idea. They'd have to prove it was theirs entirely or something.... essentially there is no way that you can get in trouble for using someone's friendly advice... or unfriendly advice for that matter
