could be many things, check ur fuses first. if that seat belt starts bothering u a lot, just close ur door, pull the seat belts back as if u were driving, and right underneath the passenger seat, there's the seatbelt control module, just disconnect it. and then use the seat belts manually.

it'll get rid of the annoying seatbelt beep and the light on the cluster.

for the radio, 95% chance its ur fuse.