Legal worries for my Greater Noida 3BHK upgrade

Since January I've been shortlisting flats for an upgrade from my 2BHK in Delta 1. I'm looking at places near Yamuna Expressway, maybe Greno Green Realty or Amrapali Silicon City. How do you guys actually check RERA registration status properly? I'm worried about those tricky builder-buyer agreement clauses... is RERA even effective if a builder delays possession? Trying to protect my investment, honestly not sure.