The maverick 88 is basically a cheaper mossberg 500. The safety's on the trigger guard instead of the top, and the fit and finish is a little bit less, but they're pretty much the same gun. That being said, no, they're not pistol grip shotguns. However, there are plenty of kits for pistol grip stocks for both the maverick 88 and the mossberg 500.
Actually, Yes, it is sold as a pistol grip configuration along with the more expensive Mossberg 500, which has the safety on top of the receiver rather than a push-thru button on the trigger guard like the older Winchester 1300 (which was also available as a pistol grip with an 8-shot magazine) - both are sold full-bore for slug or buck.
The Maverick is Tex-Mex while the new Winchester is made in Turkey. The old Winnie was a "Speed-Pump" which sped up the action with the recoil doing most of the work ejecting the shell so that the shooter had only to move the grip forward to rack the next load.
IMHO, For home protection or as a street-sweeper, both are preferable to the Mossie configuration safety-wise. Both the Maverick and the old Winnie are excellent hip-huggers but the Winnie shooter could use some practice to get used to the gun doing half the work.
Never?
Unlikely
You can purchase the pistol grip for a Stevens model 67 series E 12 gauge shotgun at most gun stores and at most gun shows. You can also purchase this type of accessory at hunting supply stores.
You cannot purchase a pistol grip for Hatsan/Escort shotguns. It is illegal to sell/buy pistol grips for any shotgun mfg. outside of the United States.
Yes
chuck Norris
A pistol grip shotgun, according to the ATF, is rulled as "any other firearm" and the buyer must be 21 or older to purchse..
No
The first known pistol grip shotgun is called a backpacker shotgun, with a shorter barrel, and shorter overall length. This is a very popular version of the shotgun, mostly purchased for home defense.
20 and up
100-400 or so
no