a few people asked but had a few other questions so the people that answered mostly just answered the other questions, so im here directly asking:

what does the 7 insight door do? what "changes above surface"?

i spent 3.9k echoes twice and i ran through the map each time and didnt notice any certain changes. 

I read somewhere that it resets items you have picked up, I might checked it later to confirm it

I believe it respawns certain non-respawning enemies and resets certain items you've picked up.