Land sold to 3 different buyers

Yes. with their percentage of share in the property.

If assessee can get a copy from purchaser it would be better, otherwise file return with first name.

Check if TDS was deducted by the purchasers?

As the value is more than 30 lakhs, Sub registrar would have sent the details of the transaction to ITD. So, check the AIS & TIS report for purchasers' details.

No that is not correct. The value is reported based on registered deal not over purchasers' shares.

In that case you must fill the data for all three registries.

How can you fill single entry when there are three different transfer cases?

You must get the names of all three purchasers with their PANs to report it in Schedule CG.

Well, that is the real story, but based on whatever information you have; file return before 31st. As and when the detailed information is available, you can revise it (till Dec. 2023 without any fine)...

Ask your client to get copies of the sale registries from Sub-registrar office. Being party to the documents he is authorized to get its copies.

Good Luck.                  ...