Lease vs power (how to purchase flat on full ownership)

Hi guys, i am looking forward to buy a flat but i am very much confused between the two terms lease and power. As per government's notice, the lease is ban on the flats and one only needs to purchase flats on power.

How one can purchase the flat (old)-10+ years without any concern of getting trapped with the power issue.

Besides, please let me know what documents do we need to have for purchasing the flat and how can we validate and verify the authentication of the documents
I would be glad to receive your response and sincere advices.

Thank you