REFUND OF RENT AFTER EXECUTION OF TENANCY:
In a tenancy contract, there is no refund of rent after payment. If the tenancy surrenders before the contract is executed, the landlord may return the amount gained which was let out during the subsistence of the tenancy which was surrendered, apart from that, a tenant is not entitled to refund of rent -

Abdurahman v. Thomas (2019) 12 NWLR (pt 1685) 107 SC @ 129, Nig Con. Holding Com. Ltd v. Owoyele (1988) 4 NWLR (pt 90) 588 @ 603

WHETHER RENT IS REFUNDABLE UPON RETURN OF KEY:

The mere fact that the tenant returned key does not mean rescission of the tenancy. Where tenant returns key before the expiration of his rent, he is not entitled to refund of rent except the property was let out, and it is only for the remainder of the period let out and paid for by the new tenant within the period under by the old tenant - Abdurahman v. Thomas (2019) 12 NWLR (pt 1655) 107 SC @ 123 and 124.