RERA registration: Is it just a paper formality?

Visited Suncity Vatsal Valley Independent Floors 1 last weekend, and it got me thinking. My wife really liked the layout for the kids' room, so we're serious about a 3BHK in Gurugram, maybe along Dwarka Expressway. But I'm honestly quite nervous about the legal side, especially with builders like M3M. How do you actually verify their RERA registration beyond just checking the number? What red flags should we look for in their legal track record? And if there are delays, which seems common, what are our real legal options under RERA? Is it actually effective, or just on paper? Want to protect ourselves from any potential traps.