RERA registration: online status isn't enough.

Looking at 3BHKs around Greater Kailash, maybe Altura GK2 for my growing family. My wife's priority is safety for the kids and a good school nearby. How do you guys actually verify a builder's RERA registration? Like D S properties, I've heard mixed things. Should I trust their online RERA status or dig deeper? What happens if they delay possession, is RERA effective then?