Am I entitled to demand the return of my money with its profits, after a person took it from me to invest in buying a plot of land that was later revealed to have been seized by the state?

The buyer is entitled to claim the full price he paid, as long as he was unable to take possession of the land. He is not entitled to claim an increase on it for the previous period. However, if the currency's value has significantly and unfairly decreased due to flotation, the more preponderant opinion is to consider the currency's value at the time of settling rights if there has been egregious deception (ghabn fahish) or a currency collapse. This is estimated based on the value of essential goods or the price of gold.