Claiming refund for delay in property handover after full payment

I have bought three apartments in a project and the delivery date was in 2018. I have paid 100% and nothing is pending.

The builders informed me that the delivery will be in July 2019 but now they are saying the end of Dec for one apartment and the rest in 2020.

If I want to withdraw and cancel the contract, can I get the complete refund and will I receive the interest too?