Property late registration selling now

Based on agreement and possession; it will be long term holding.

the problem you might face is that the registration done with the builder will end up reporting in the latest AIS statement. So if you report the sale as long term capital transaction, a good chance of Income-tax department seeing this is a discrepancy and issue you a notice for the same.

So be prepared with facts/documents as well as legal precedents for your tax position. 

thank you. but legally it is acceptable? have all documents from developer.

the general position is provided above. If there is anything in your documents that could be detrimental to your position, it can only be determined after a proper review.