Not much younger than you, but I got you on the definitions.

I’d say based is more or less the opposite of the kids calling things cringe. Speaking truth to power is definitely based.

Cap means a lie or posing. It can be used as a verb to accuse someone of lying to (i.e. “You’re capping”). To say no cap means “I’m dead serious”.

Bet is basically an analog to ok.

This slang all essentially comes from hip-hop and the surrounding culture around it.