Is the money that a grandfather deposited in the bank in his grandson's name before his death, and regarding which there is a suspicion of unlawful gain, considered an inheritance or not, and is it permissible for the grandson to take all the money (without interest) or part of it equivalent to the amount of unlawful gain suspected, and to whom should the bank interest be given?

If the grandfather placed money in the bank in your name as a gift during his lifetime, and you took possession of it, or your guardian took possession of it, then the money is yours, and you are not obligated to dispose of it merely due to a doubt about its impermissibility. However, if the gift was given during his death illness, then it is a bequest. If you are an heir, it depends on the approval of the other heirs. If you are not an heir, it is valid unless it exceeds one-third. If it was a gift given during his lifetime and you did not take possession of it until he died, then it is considered part of his estate. The interest should be taken from the bank and spent on charitable causes with the intention of disposing of what is unlawful.