Is it permissible to dispose of a financial deposit and then collect the amount and return it to its owner when he requests it?

You must safeguard a trust as you would safeguard your own money. Mismanaging it is a breach of its safekeeping and necessitates guaranteeing it, even if it perishes after being placed in its secure keeping. You must seek forgiveness from the owner of the trust for what you have done, and give him the profits if he does not forgive you. Do not repeat such an action.