(1) If you have not bought that plot then no zakah shall be wajib on it. In case you bought the plot and intended to sell it while buying and yet the intention is intact then zakah shall be wajib on its value.
(2) Yes, zakah shall be wajib on this money if the conditions which make zakah wajib are met. Zakah shall be wajib on the amount you have deposited as instalments provided the conditions of zakah are met.
(3) If you have bought those plots and intended to sell it and later on there was no changes in your intention rather the intention of selling still remains then zakah shall be wajib on those plots. If you did not pay the zakah of many years then you should evaluate the value of each year and pay the zakah. And if you have not bought those plots rather it was inherited by you then no zakah shall be wajib on their values right now.
Allah knows Best!
Darul Uloom Deoband