Are the modifications to the electronic game—which contains Sharia prohibitions such as magic, the presence of deceased characters, and an idol—sufficient to remove the ruling of prohibition, or must the game be deleted entirely, and will the publisher of the free modified game be rewarded?

If the religious prohibitions are removed from the game, there is no objection to playing it. You are hoped to be rewarded for that if you intend to divert players from those prohibitions.

It is not permissible for a player to play with someone whom he knows the game involves religious prohibitions for him, lest he assist him in disobedience.