The Polymorph spell states "The target's game statistics, including mental ability scores, are replaced by the statistics of the chosen beast."

Consider the situation where a spellcaster PC Druid with the warcaster feat polymorphs themselves into a Giant Ape.

Q 453 What items are specifically included in Game Statistics?

Q 454 Do game statistics include abilities from classes or does a polymorphed PC retain these?

If they do lose them then would not the spell caster lose the Spell casting class ability and the polymorphed caster would instantly revert to their normal form. ( I accept that the Polymorph spell separately and specifically prohibits speech, spellcasting, and actions with hands or speech)

Q 455 Do game statistics include feats? If the Polymorphed Giant Ape had to make a concentration check after sustaining damage would it roll with advantage because of the warcaster feat?