Yes they are the same clip.
You should not have to push on the clip. See the owners manual at the link below. Your C11 may have to be repaired.
The Air Mag C11 (Airsoft) is designed to shoot 6mm Plastic BB's. The C11 BB pistol is designed to shoot .177 Caliber metal BB's.
Crosman still services this pistol it is best to contact them and tell them what you need, their address is: Crosman Corporation7629 Routes 5 & 20East Bloomfield, NY 144431-800-7AIRGUN (724-7486)
The C-11 shoots .177 Caliber BB's not pellets
No they are all the same.
Yes, the TSD Sports NBB 1911 is compatible with the Crosman Airmag C11 magazines.
The c11 co2 pistol shoots at 480 Feet Per Second (FPS)
No it is designed for BBs only.
there is no hop-up system on a Crosman C-11.
The C-11 is a BB gun. The other two are pellet pistols. Of the three I prefer the 357 it is more accurate than the other two pistols.
The best way to decide is to read the owners reviews. See the links below and scroll down the page when it opens and read each owners review.