How did the WR record only stack 28 blocks?

Other records stacked 31 or 32 blocks to reach the build limit.

Does a video must have sound?

I got 26.532 seconds and noticed that there is no sound :(

I want to speedrun this game and I have the Korean version.

Which region should I submit my record to?

I don't see Korea in the Region field.

Which record is the correct one? I'm confused.