(1) Yes, (2) Maybe, maybe not.
The MKI 's will accept the MKII mags. If you have an older A-54 frame,, the follower button is on the right side.
The later A-100 frames, have the follower button on the left side. All MKII mags have the button on the left side.
If necessary, just swap the button & have at it! It's not hard to do.
Depress the follower, pull the button while holding compression on the follower. Move it to the other side, and relax. Start shooting.