Agreement to sell UDS followed by Sale Deed Registration

Dear all, I plan to sell my UDS in a property that has now demolished it's old building and has currently restarted development of the new building after getting approvals. The proposed buyer is not a part of the old association or the new association. The proposed buyer is an outsider attempting to buy this property from me. The buyer is willing to pay a price of 20 lakhs for the UDS registration in total, and is.also willing to bear the costs of registration, lawyer fees and he is also willing to pay me for all the previous dues I have paid towards the plan approval charges for the new redevelopment, etc. totalling to 60000. My queries are: 1. The buyer is planning for a bank loan from a leading private bank. So he wants me to enter into an agreement for sale for 10 percent payment as advance - 2 lakhs - and for a period of 3 months, within which he is agreeing to complete the sale deed registration process by paying the remaining 18 lakhs. He wants to make the payments of dues that I have paid in the past towards planning charges etc. via a separate cheque that is not a part of the agreement to sell or the sale registration deed process. Can I execute an agreement to sell and accept the advance of 10 percent? 2. If I choose to execute an agreement to sell with the buyer, do I need to insist on registration of this agreement to sell document as well? Currently the buyer says that there is no registration needed for an agreement to sell, and that within the 3 month period of the agreement to sell, he will execute a registration of the sale deed. Is he correct? Or should I insist that we register the agreement for sale as well and then we do the sale deed registration within the 3 months as well (basically, two registrations, one for agreement for sale and one for sale deed registration). 3. The agreement to sale has no clause regarding forfeiture of the advance payment in case the sale deed is not registered within 3 months. Is this okay? The buyer says he will just take the money back from me if he is unable to complete the registration and then cancel the agreement to sale. But I feel like this is unfair to me because I am waiting for 3 months for him and also executing an agreement to sale for him. Please advise in this regard. 4. If we do not register the agreement for sale and later we execute the registered sale deed, mentioning the agreement for sale as part of that document, will the registrar office in tamil Nadu object and refuse to release the land documents in favour of the buyer? If yes, can the buyer prosecute me for failure to guarantee unencumbered ownership of the property? Please advise. 5. Are there any other risks? Thanks for your support. I have seen articles online about a change in the laws that mean that now, even agreements for sale need to be compulsorily registered in some states such as Maharashtra. But I do.not know the situation for Tamil Nadu. Hence this query. Thanks for your support.