The best way to destroy a Steward is to go into box forum and bash into them. They will fall over and maybe turn into junk. Be in time though, Stewards have an electric shock built into them.
When you are playing the mission where you have to get some Blue Cells to open a door and join Eve, enter the room where below you there is a magnetic cube area. Pick up a magnet cube and throw it and any door or something close to the panels that the box below has to touch. When a door opens, head straight into there and do the puzzle to unlock the door where that robot is. When you have done that, pause the game, go to options and turn the music off. Then resume the game. Now you can turn on Wall-E's radio so the Axiom Bot can follow you without music.