You must unlock and then buy them.
to get the robot in Lego Chronicles you must achieve 100% in the game.
complete the game (100%)
you don't have to do anything after unlock him but you could destroy the city.
Monkey
no there is not
No.
p164
get 100%
yes
Shoot 100 agents.
By beating King, Act I.
No. He is not on the character list, nor is he a cheat code.