Can the Action Surge be used to cast another spell during the same turn?

Is Elemental Adept the only feat you can take more than once?

Does Catapult spell damages the creature if it succeeds the Dex saving throw?

If a mount takes the Disengage action does the rider provoke opportunity attacks?

Aaarakocra Monk Unarmored Movement

Does a fighter with an increased crit range (say 19-20) always hit on a 19?