Is it permissible for a person to distribute tapes and write on them that their reward and recompense are for all deceased Muslims? Is it valid for the reward to reach all deceased Muslims? And will the one who does so be rewarded?

Distributing beneficial tapes is an act of righteousness and spreading knowledge. Its doer is rewarded in two ways: spreading knowledge and dedicating the reward to deceased Muslims, for creation are Allah's dependents, and the dearest of them to Him are the most beneficial to His dependents. There is no impediment to the reward of a deed reaching the deceased if it is dedicated to them.