Originally Posted by chamber-music
Many people have brought this one up and its been explained multiple times.
They never said Charles and Erik invented Cerebro and the version Hank invented was destroyed. Professor X and Magneto may of built A
Cerebro meaning the version we see in the Singer X-Men movies most likely.
Your other points are valid though
How? They part ways at the end of First Class right as Professor X is opening up the school for more students. The Cerebro at his mansion is not built yet, and the only person who could have helped him built another Cerebro at the school was Hank by the end of First Class. But I could be wrong, maybe the built they built a version of cerebro at the school but we just don't see them do it.