You can only control one brother at a time. Switch between them using the hotkeys or by clicking on the character.
No, you can only control one brother at a time. Moving one brother will automatically switch control to the other.
Use both brothers to connect or merge elements in the environment to overcome obstacles and progress through the levels.
Try exploring different paths, or use one brother to set up a solution that the other brother can use. Also, check for any hidden objects that could help.
Collectable items can be picked up by walking over them with the controlled brother. Items can be used to solve puzzles or help in the journey.