But above MAX_MONEY value's sanity check, how it work?
For instance by declining any transaction including an amount larger than MAX_MONEY
if (txout.nValue > MAX_MONEY)
return state.DoS(100, false, REJECT_INVALID, "bad-txns-vout-toolarge");
https://github.com/bitcoin/bitcoin/blob/3c098a8aa0780009c11b66b1a5d488a928629ebf/src/consensus/tx_verify.cpp#L176Follow bob123's advice from above and do a simple text search on Bitcoin's repo.
And what happen pre-mine 100% of coin and still mining reward is not 0?
...then you probably didn't set the mining reward / block subsidy to 0?