Hello i need help

[FONT=Comic Sans MS]Hello,
1° i need to know if the enemy blueprint for a 2D sidescroller game is the same than a 3D game(FPS, RPG, etc.)
2° If its diferent how i can create one, if its the same how i can apply to a 2D sidescroller
3° how i can make the enemy follow the principal character
Thanks for ur reply´s and have a nice day.