Site Development agreement

Hi Sir, I have a site in Andhra Pradesh, Recently I approached a developer to build an apartment with 50-50 shares (a total of 4 flats). The developer suggests the following process. 1. I have to register half of the land as an undivided share to his party 2. Developer will deposit the market rate into my account 3. I have to deposit the amount to the joint account ( Myself and the developer) 4. Developer will take few vouchers in my name for the transferred amount ( for the income tax process). 5. Register the partition deed. 6. Plan approval. The developer has suggested this process to avoid the GST for a development agreement. Now I insist on the construction agreement with agreed specifications of the flat and timelines to complete the projects with a penalty on a stamp paper of Rs 100 without registration. Please clarify the following points: 1. If the developer did not complete the flats or not started the project after I register half the land in his name, what is the process to get it back legally. 2. how valid is the construction agreement without registration in the court of law. Regards Satya