To find a way inside the castle in level 3 of LEGO Marvel Super Heroes 2 go over to the cage to the left of the gate. Switch to Doctor Strange and use time controls to fast forward the time until the cage is broken on the ground:
Switch to Groot, make Groot get large and enter the cage. Switch back to Doctor Strange and wind time backwards until the cage rises high enough. Switch back to Groot, exit the cage and open the gate by spinning Groot forwards.
To hit the switch by throwing and bouncing Captain America’s shield at the right angle to open the door in level 2 of LEGO Marvel Super Heroes 2 move the stack of boxes in the right part of the hangar forwards:
Then go back towards the hangar doors and stand on the podium that looks like Captain America’s shield:
Aim the shield at the left bounce pad and throw it:
To get up the cliff in level 2 of LEGO Marvel Super Heroes 2 switch to Thor and fly up to the top of the cliff. Use She-Hulk to break the glowing box in front of the door and build the platform:
Switch to Captain America and stand on the platform:
Switch back to She-Hulk and use Captain America to get a boost up to the handle. Use the handles to climb to the top of the cliff. Go over to the buttons to the left and stand on them with She-Hulk and Thor:
Switch to Captain America and build a fan. Use the fan to get Captain America up the cliff.