How much can I find out about my birth parents without seeing my adoption papers?

I don't know.. and the unknown may not be what we want it to be either.. chances are that your birth parents may not have even been together relationship wise .. sometimes they are young and single and broke and they why they give up their child and hope they go to a better more stable home.. and some do have a happy adopted life.. not always tho unfortunately

Then how have you come to know?

You are obsessed and I will say goodbye to your trolling