Is it permissible for Abdullah to reside in the shared villa, which has not yet been sold, and is he entitled to benefit from it alone without the other partners, and what should be done if its sale is delayed?

The two partners in the villa: it is not permissible for either of them to act in a way that harms the other. If the occupancy of one partner causes harm by hindering the sale, then he is not allowed to do so. He must pay rent for the villa for the period he occupied it, commensurate with each partner's share.