Is zakat obligatory on a frozen investment deposit that cannot be disposed of, and on its annual return which is not determined until the end of the year and has no minimum limit, and is this return halal?

The answer to your question can be summarized as follows:

1. Ruling on Usurious Returns: If the bank is usurious, the return is unlawful because it is usury (riba), and the client is considered a lender to the bank with interest.

2. Repentance and Disposal of Funds: You must repent and withdraw your funds from the usurious bank. If you cannot find an Islamic bank and fear for your money, place it in a current account without interest. It is not permissible to deposit money in a usurious bank except out of extreme necessity.

3. Disposal of Unlawful Returns: You must dispose of the usurious returns by spending them on charitable causes. Zakat is not due on such returns because they are unlawful money; rather, Zakat is due on the deposit itself.

4. Zakat in Islamic Banks: If the bank is Islamic, Zakat is due on the principal amount deposited and on the returns generated from it, provided it reaches the nisab (threshold).

5. Obligation of Zakat Despite Inability to Withdraw: As long as you were paying Zakat on the principal amount deposited, you have done well. Your inability to withdraw the money does not negate the obligation of Zakat on it when its conditions are met. Zakat is due on the balances of investment accounts and their profits if the conditions are met, because you deposited the money by your own choice.