How do i do the challenges in ninja gaiden 2 for the weapons?

in order to get the achievements for beating ninja gaiden 2 with only one of the weapons, how do i do that? do i just beat the game and then go through it again using only certain weapons?|||As stated above you must do a new game+ to have all your weapons to start off with. Here is where the controversy comes in. Some people say that it is alright if you hit enemies with other weapons as long as the killing blow is with the weapon you are going for the achievement for. Some say that all damage needs to be done with the one weapon. Personally I do not know which is true but I would go with the second just to make sure. There are two parts int he game where the game auto equips a different weapon. Do not think it is safe to use these weapons. When this happens you MUST switch back to your weapon for the achievement.|||Once you beat the game, you can play through the same difficulty again with all your weapons and gear. Just make sure you only use whatever weapon you are trying to get an acheivement with.