Is zakat obligatory on a communal land (Ard Masha') whose location is unknown, and the owner's intention for it (whether for building or trade) has not been determined, given that it has reached the nisab? And can the payment of zakat be delayed for someone who does not possess its value?

You are not liable for Zakat on the land as long as you are hesitant about the intention to sell it for trade. Zakat only becomes due on its price after a full year has passed since its sale. If Zakat becomes obligatory for someone and they are unable to pay it, it remains a debt upon them, to be paid as soon as they are able. They are granted a delay until they sell the land and pay its Zakat for all the past years, according to its value at the completion of each year.