Any hellp would be highly appreciated because I buying a house without assistancea nd on my own

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My under-construction flat is almost complete. The home loan was a part-payment type. The builder is asking for the full and final payment for the flat.
I have to provide a letter to the bank for this and would like the eligibility for a complete flat for a full dispersement of funds by the bank before this.
Kindly help with any details urgently.