How is it possible to revoke a power of attorney after misusing it?

Sir,

I wish to know about the general power of attorney in Dubai. I made a general power of attorney in my brother's name. He renewed it until 2016. Its court stamp expired in 2016.

My brother used it to sell my flat in 2017 and afterwards, he gave the same to a real estate agent to get rent from 2016 - 2021.

This general power of attorney, which had been once used in selling one flat and which the court's stamp expired in 2016, can it be used for getting rent without my knowledge although its date was 2016?

In 2021, I came and cancelled it. But the rent real estate agent got through it, can this be recovered?

If a general power of attorney can be used even without renewing, then why there is a law to renew it after every two years?

The agent says, it remains usable and working until it is cancelled. No matter even if it is not renewed it can be used.

I am worried if my brother makes a fake agreement with a person in backdate and write receiving of money on my behalf, what will I do? Any remedy also?