When you go past the gate to go to the next area, you should see Mike trapped on a block in the far back. Use Relic Detector when you see the pink sparcle. A boomerang slot appears on Mike's block. Throw a boomerang to save him.
When you continue the story, there is a stretch, where you see all from bird view. Look for a Silver Lego platform to blow up. It's the entrance to the secret room. Go through. There use stealth to go past the camera to get the minikit.
To open the door to the right with the green light, use Pole Vault on the missing pole slot. Jump on the poles to open the door. Go through. On the other side, push the statue over the edge (thats for minikit 10). Don't leave yet. Go to the right and turn the switch. The fire blocks should turn and are now passable. Now go back through the door, over the now passable blocks to pick up the Minikit