Every currency in history got printed into worthlessness. Bitcoin is just software — so open it up and give yourself some. Who's going to stop you?
You're a miner now: your job is to write the next page of Bitcoin's record book. What is Bitcoin mining?
Simplified — the real rulebook has hundreds of checks. They all fail you just as fast.
So the rules can NEVER change?
They can — Bitcoin's software has been upgraded many times. But a change only happens when essentially everyone opts in voluntarily; nobody can decree one. Dissenters can keep the old rules, and anyone can copy the code and launch a 42-million-coin version — thousands have. A “Bitcoin” with a different cap simply isn't Bitcoin, and markets price it accordingly. The cap is safe not because change is impossible, but because this change has no constituency: it asks the holders of 21-million-capped money to vote themselves poorer.