Is it permissible to purchase a car in installments from the Agricultural Development and Credit Bank, where the bank buys it for cash price and adds interest to sell it in installments, with half the value paid upfront and the remainder guaranteed by possessing agricultural land?

If the transaction involves the bank purchasing the car and owning it, then selling it to you in installments, the sale is valid and permissible. There is no objection to the selling price to you being higher than the purchase price. The important thing is to ensure that it is a real buying and selling operation and not an interest-based loan. Furthermore, there is no impediment to mortgaging land or other assets with the bank until the installments are paid.