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?
Yes, it is very possible to increase the supply of the bitcoin or make it more or even make it infinite but the thing is that it is very hard to crack the code because you will also do the re-arranging of the blocks which is even the smartest people can't do that thing. So if you are asking if it is really possible to increase the supply then probably the answer would be "Yes" but it is kind of a hard job to that thing. Just think why the government didn't print so much paper money? it is because there is only fix money that we need to be circulated.