Who are the earliest unlockable characters that will give me all the exploration powers in LEGO Harry Potter 2?

Question

Which unlockable characters in LEGO Harry Potter Years 5-7 are the earliest unlocks for all the exploration powers (such as Dark Wizard)?

Answer

• Strength - Dudley: Year 1 level 1. Alternatively, use the super-strength red brick found in Hogwarts.
• Dark Magic - Bellatrix (Azkaban): Year 7 part 2, in the air over the field near Hagrid's house. Use the pink platform with Hermione to get the pumpkincopter, then use it to fly around and get Bellatrix.
• Key - Mrs. Cole: Year 7 part 2. Use dark magic in the diner kitchen to unlock her.

Check more discussion of this question.

How do I open the barred door in the Derelict Row sewers?

Question

There is a door in the Derelict Row sewers that clearly has an area behind it, but does not open. Is it part of a quest or do I need to find a switch/terminal? I am still in act 1.

Here is an image from the Deus Ex wiki, where I have circled the door in question:

Answer

If I remember correctly, assuming that that door is made out of bars (which I'm guessing is correct seeing as you say you can see there's stuff behind it), then it's used later on in the game as an exit back into this section of the sewers

In a quest you'll progress into the section you can see on the other side and that door will automatically be opened to give you a way out.

Check more discussion of this question.