Is this bike good for a beginner learning tricks?

Yes. The rotor, pegs and low gearing suit a rider learning spins and grinds. The steel frame is heavy, so it is not the lightest choice for advanced tricks.

What does the cable detangler rotor do?

It lets the handlebars and fork spin all the way around without pulling the brake cables tight. That makes barspins and tailwhips possible without stopping to untangle cables.

Does it have a coaster brake?

No. It stops with front and rear handbrakes, and the levers adjust to fit smaller hands. A rider used to pedaling backward to brake will need to learn hand braking.

What size rider fits a 20-inch BMX?

20-inch wheels are the standard size for kids roughly 7 to 12 and around 4 feet to 4 feet 10. Smaller or younger riders usually need an 18-inch bike.

Yes, it has one 32t x 14t gear. That is easy to pedal but limits top speed on flats and makes steep hills hard work.

What comes in the box?

The bike with front and rear pegs, a kickstand, and front and rear handbrakes with reach-adjust levers. It arrives partly disassembled and needs the bars, front wheel and brakes set up.