easy
for the tank pick up the rock and put it in the nozzel of the tank, for the ghost letters spell out "ninja kami". for the helicopter, pick up the car and throw it at it right away. for the robot duel, just take out the supports and attack the big guy so he moves and falls half way, then get out and take the last supports.
 "Factory Balls 2"){kind=icon}
 "me and the key"){kind=icon}
 "Bowja 3 - Ninja Kami"){kind=icon}
 "Learn to Fly"){kind=icon}
 "A Small Favor"){kind=icon}
 "You Have To Burn The Rope"){kind=icon}
 "The Visitor"){kind=icon}