NLHE RULES Q - What conditions betting reopened after allin?

Hi,

I apologize if this is answered elsewhere, but I would appreciate if my rule question could be answered.

At my local home game, we seem to be in confusion over how much the minimum raise must be for an all-in to to reopen the betting.

E.G
(1) A bets 50, B calls 50, C all-in for 90 total - betting reopened?
(2) ", ", C all-in for 75 total - "?
(3) ", ", C all-in for 110 total - "?

In no particular order, and if anyone can think of any more scenarios that may be confusing, please add to it!

Thanks in advance!

For betting to reopen the all-in has to be a minimum raise

1) If the initial bet was from 0 - 50 and then the raise is only 40
2) This is obv if 1 doesn't reopen the betting
3) This reopens the betting because the raise is 60