What age or height is the Impact 24" built for?

It is a 24-inch wheel bike, which generally suits kids around 8 to 11 years old or roughly 4'2" to 4'9" tall. Check the standover height so your child can put both feet down.

Yes. It uses a 7-speed Shimano drivetrain with a rear derailleur, so it handles moderate hills better than a single-speed kids' bike.

No. The fork is rigid, which keeps weight and maintenance down. It is fine for paths and light trails but not for rough, rocky terrain.

What brakes does it use?

It has V-brakes on the front and rear. They are easy to adjust at home but are less effective than disc brakes in wet or muddy conditions.

Is it worth it over a cheaper single-speed bike?

If your child rides hills or longer distances, the 7-speed gearing is the main reason to choose it. For flat neighborhood riding only, a simpler single-speed bike would do.