Electric sub and main panel

I inspected a sub panel that was installed next to the main electric service panel. The home was constructed in 1983.

The sub panel did not have any neutral or ground wires attached to the neutral bus or ground bus. The bus bars were installed and separated in the sub panel. Only a green ground wire was attached to the ground bus in the sub panel. The neutral and ground wires for the sub panel were attached to the main electric service panel bus. This I have never observed before. Is this acceptable?

Also, a ground wire and neutral wire were attached under one screw in the main electric panel. Should they be separated and installed under their own screw?

Well Michael, I can tell you for sure that neutrals must each terminate alone under it’s own screw. Neutrals and grounds can terminate on the same bus bar, but not under the same screw.
Long as each circuit has a path back to the pole that includes connection to a main bonding jumper in a modern service, I don’t see why neutrals need to be routed through the sub-panel, since they have to be isolated there anyway, but I’m going to leave that one to be confirmed by others.
The green wire probably bonded the sub-panel cabinet.