subject-verb agreement

[blue_jeans_vb]

1. When will he bake a cake?

2. When will the game starts?

3. What did he builds?
I think no. 3 is incorrect.

Do I always have to follow subject-verb agreement even in interrogative sentence?

[Kondorosi]

1. When will he bake a cake?

2. When will the game starts?

3. What did he builds?
I think no. 3 is incorrect.

Do I always have to follow subject-verb agreement even in interrogative sentence?

When we have a verb phrase, and not only one verb (will start), only the first one is finite, that is, only the first can be inflected for person.

The game will start when. Will has the same form for all persons. Will, will, will, ...

When (the 3rd person singular of will = will) will the game (game = 3rd person singular noun, subject) start.

Agreement means this:

game = 3rd person singular noun, subject
the 3rd person singular of will = will

...will the game...