Builder-buyer agreements still hide nasty clauses

My lease ends in 3 months and we need a bigger place for the kids, eyeing a 3BHK in Noida Extension. How do you actually check RERA registration beyond just the number? Are there specific red flags in the builder-buyer agreement that still favour them, even with RERA? We're looking at V.R.Buildtech's NS Green Valley. Any advice on what to watch out for legally?