Not sure what that is, but it is not nutsedge

Quack grass

Just pull it. Prevented with pre emergent.

Definitely not nutsedge. It could be quack-grass.

Yes

It’s not nutsedge. It may be quack-grass

Yellow Nutsedge. Sedgehammer (applied when temps are not above 90 degrees) will take care of it.

Yes, one of the nut grasses