On the new version, the fourth challenge has become impassable. Instead of a gun, it summons many mobs and speeds up all enemies on the field. Also, now you need two of mine to kill one regular enemy. Because of this, this challenge became impossible to pass. Can you send me a way to download the old version or a guide?

try to send the bomb guy at the enemies that are closest to your house and if there's no monster near your house send the bomb to the boss
if you can't send the bomb at the enemies put another thing
hope this tip helps