Is zakat obligatory on a plot of land that was purchased to preserve wealth, and if so, is it retroactively due for two years, and on what value is the zakat calculated: the purchase value or the current value?

Zakat (definition) is obligatory on land purchased with the intention of sale. It should be valued and zakat of 2.5% paid on it upon the completion of a hawl (lunar year). Zakat is not obligatory if it was purchased with the intention of acquisition (ownership for personal use). If the buyer is undecided between selling and acquiring, then their predominant intention should be considered. If they purchased it for acquisition and then later intended to sell it, then its value should be subject to zakat if a hawl passes from the time the intention to sell arose.