Noida buyers: How do you verify builder credentials?

Did a site visit to AIG Aigin Royal in Noida Extension last weekend. Kids have moved out, so we're looking for a smaller, manageable 2BHK flat. My budget is around ₹85L. Honestly, I'm worried about builder delays and legal issues here. How do I properly check a builder's RERA compliance and their past track record? Ambesten Homes seems okay, but you hear so many stories about possession delays. What are our actual options if possession gets delayed? Is RERA truly effective or just on paper for Noida projects?