1. Hope you want to mean GPA by saying it GP. The person who has executed the GPA only can correct it or alter it. Sale of property through GPA has been ordered against by the Supreme Coutrt. The Developer/Owner should have exeuted and registered a Sale Deed in your favour. Contact him now and ask him to register the sale deed with correct Survey Nos. by paying the reuired stamp duty and registration fee,
2. You should have conducted search for it before buying th plot. Contact a local Amin who will be able to guide you. You can also contact a local lawyer for this purpose,
3. Better pay them money and get the mistakes corrected,
4. No. Govt has nothing to do with your mistake,
5.No. Contact the developer or his legal heirs (if he is not alive) to register the said plot in your name,
6. Possession of a plot s given by the person who sales the said plot. Contact the developer or his legal heirs.