Documents to keep on house property sale?

On closing the deal on selling my house property, what documents should I keep regarding the transaction? Should they be originals and certified or are photocopies OK? The implications I am looking are as proof for tax filing as well as proof of transaction. Do I need some document on what all cheques were received.

Would the property dealer provide these documents automatically or I need to ask for them.
This question is specific to Indian context around Noida.

Want to retrieve complete chain of property transfer documents?

I am trying to take loan for a flat and the bank’s legal dept has verified that the property doesn’t have any problems but has asked for the photocopy of the chain of property transfer documents.The builder doesn’t have the complete chain of property transfer documents. Where and how can I get this chain of property transfer documents?? Please help its very urgent..
I am trying to buy the flat in west patel nagar, new delhi

What tax documents do i need as a sole proprietor who is importing into india?

I have just applied for iec and i’ll be importing different types of products and raw materials into india. I will be using my residential address as office. What kind of tax documents do i need? I’ve heard that sales tax is required for those whose turnover goes beyond 10 lacs. I have no idea about taxes. I do have a pan card if that’s something you would want to know. Thank you!