Must zakat be paid on money that has been frozen for ten years now, and is it permissible to pay it in installments if the estimated amount changes?

You are obligated to pay Zakat (definition) on this money for all the past years, as Zakat does not lapse with the passage of time. You must hasten to pay it without delay, unless there is an excuse. You must ascertain the amount of Zakat to the best of your ability. If you can obtain a bank statement, that is required. If it is impossible to determine the exact amount, then act based on your best judgment and pay what you believe to be the Zakat due on your wealth.