[Jinksy]

After the auction 1M 1a 2C 2D 2M, which bids by responder are forcing? My current guesses:

2N seems like it would be useful both as natural invite and as forcing.
3m might depend on whether you're playing IJSes? If so, it's surely weak, hoping to play there, if not I suppose it needs to be forcing.
3M seems like it should be considering you still don't know if opener has 6 of the suit, so given that you didn't raise them the first time you either have 2 card supp or a 3 card limit raise (not sure about this - bit rusty on 5cM 2/1)
3oM must vary depending on both the initial sequence and whether you play 1H 1S as a WJS, but is presumably natural where that makes sense and normally GF or at least F1 over 3H.
4m doesn't exist? Can't see you suddenly having a hand that wants to slamhunt in the major, you've had your chance to force in the minor, and without a known fit you're obviously not bypassing 3N.

[Free]

After 1M-1NT, responder can't have a forcing hand anymore. So after opener's 2M rebid, all bids are weak or INV. 3♣ for me is weak, 3♦ must be INV, 2NT is INV, 2/3♠ (after a 1♥ opener) is weak/INV,...

After 1♥-1♠-2♣-2♦-2♥ it's another story. I play 3♦ as 4th suit GF (since opener has shown ♠+"♣"), 3♣ is weak, 2/3♠ is weak/INV,... 3♥ doesn't have a natural meaning, so I use it as GF, probably with ♦ stopper and ♥Hx.