Does zakat become due on installments paid for an apartment not yet received, with the intention of residing in it but a current desire to sell it, and does zakat become due on an incomplete house not used for residence or rent?

There is no zakat on the installments paid for the apartment because it has left the possession of the questioner. Nor is there any zakat on the value of the apartment itself, as long as the questioner's intention when purchasing it was for housing and not for trade. A change of intention to sell is not considered trade. As for an incomplete house, there is no zakat on it. However, zakat is due on its rental income if it reaches the nisab and a full year has passed over it.