Apocalypse 5 facts you didn't know about Xavier...

1- On Earth-10005/Earth-TRN414, Charles Xavier was born in 1938, not 1932. He graduated at the university in 1962, when he was 24 years old (according to the credits of First Class).
The first meeting between Charles (12 years old) and Raven (10 years old) occurred in 1950, not 1944. The "1944" timestamp only referred to 14 years old Erik and his tragedy within the concentration camp.

2- In X1, Xavier provided a cover backstory to hide the truth about the Cuban Crisis, the fact that Magneto and Mystique once had been X-Men, as well as to protect Moira MacTaggert who, in the original timeline, never recovered her memories about the events.

3- The special serum developed by Beast was best calibrated upon Henry McCoy's altered physiology. In the long term, Xavier suffered negative and nearly-fatal consequences and was forced to quit its intake in the late 1970s. His loss of hair in the original timeline was one of the many side effects.
In the original timeline, we can see Xavier walking in two instances: the prologue of The Last Stand (1979), where Jean Grey read his mind (he wasn't using any telepathy), and the ending of X-Men Origins (1983), where he was generating a mental projection of himself which looked "upright".

4- P. Xavier, Charles' twin brother, was kept safe on the Muir Island, under the care of Moira MacTaggert Jr., the niece of Moira (from First Class). See the post-credits scene of The Last Stand.

5- So far, we had met 5 variants of Charles Xavier/Professor X:

a) Xavier Prime of Earth-10005/Earth-TRN414.
b) Xavier of Earth-17315 (Logan 2017).
c) Xavier from the Legion universe.
d) Xavier of Earth-41633 (Deadpool 2).
e) Xavier of Earth-838 (Dr. Strange in the Multiverse of Madness).