GST and Stamp Duty paid verification

Dear Sir,

I had purchased flat in pimpri chinchwad. At the time of agreement i have paid GST amount .
How should i get proof of GST i paid.
which was return by builder or not.
can i ask builder to provide GST invoice.
How should verify that Stand duty is paid by me is reflected to government or not.

please guide.

Thanks and regards,
jidnyesh