RERA compliance is still just on paper for many builders, honestly.

Been fed up of renting for ages, landlord raised rent again, so finally taking the plunge. Looking at a few 3BHKs in Gachibowli and Kokapet, even Sattva Lake Ridge caught my eye. But the legal side of things is stressing me out. How do you guys actually check RERA registration beyond just the number? Are there specific red flags on the RERA site I should be looking for? Also, if a builder like Salarpuria Sattva delays possession, what are my real legal options under RERA? I've heard stories, but is lodging a complaint actually effective or just a formality? Trying to protect myself here.