Why does my bike back wheel lock up?
A wheel “locking up” usually means a bad bearing. First step is probably to remove the freewheel and axle so you can inspect/reinstall the bearings correctly. You would need a freewheel remover tool and probably a thin wrench (“cone wrench”) to do this properly.
Why does my wheel not turn when I pedal?
There’s a chain that connects the large cog between the pedals to the smaller sprocket at the centre of the back wheel. If the chain has come off either of those, the pedals will turn but the back wheel may not. If the chain is stuck, then the pedals may not even turn.
How do you fix ghost pedals?
The end result will be sporadic ghost pedaling when the bicycle is coasting. To fix this issue, you will have to replace the broken pawls, the freehub body, or the entire hub.