RERA checks for Ghaziabad builders: What to look for?

Spent the whole weekend researching Ghaziabad projects like Sampatti Ashiyan. RERA registration is crucial, but how do you *really* check it for red flags? My parents stress verifying a builder's legal track record, especially for someone like Unione. What are the actual steps for due diligence beyond just the RERA site? Is it actually effective?