Is it obligatory to return money taken from the father under the pretext of studying but spent on other personal needs, given the inability to confront the father, and is it permissible to donate this amount as charity on his behalf, and is it a condition that it be given all at once, and will the good deeds performed by the questioner not be rewarded due to their being mixed with the father's money?

What you took from your father through lying and deception, you are obliged to return to him, unless he absolves you of it. You are not obliged to inform him of what you did; rather, it is sufficient for you to return the right to him, even through indirect means. You are not permitted to give charity on his behalf with his right. You can place what is available to you in his pocket, or with his money, until your conscience is cleared. If you do not have all the money, then pay it in installments according to your ability, for material rights must be returned to their owners or their absolution sought. You can also ask your father for forgiveness and for him to absolve you of what you owe him, without explicitly stating the reason. As for giving charity before repaying the right, if you are fairly certain that the fulfillment will come from another source, then there is no harm in giving charity, and it may even be desirable. Otherwise, it is not permissible.