So there are 21 million total because that is how it was coded. Will it be possible to increase the supply or even make it infinite if someone was able to crack the code?
Is it possible to change the code and add more coins? Yes, will it ever be done? No, bitcoin is now a one trillion dollar project and the developers are never going to do anything that could risk bitcoin in that way, this is why updates are kind of slow as they want to make absolutely sure that everything is OK before they apply an update and the same is true for the supply of bitcoin.
Yes, possible but we are running on different nodes which not under by bitcoin protocol, nothing can change the bitcoin code, if there are changes, that is not a bitcoin network. There are too many developers trying to copy the code of bitcoin and make their own coin, but it is totally different from bitcoin.
The fact is the fact, nobody can change the fixed amount of bitcoin and if we are talking about manipulating, yes bitcoin price can be manipulated but does that mean they can change the fixed amount of bitcoin.