The design and buttpad style are what helps with recoil.
The cheek riser for the FAB Defense GL-Shock stock can be found at the link below.
https://www.opticsplanet.com/mako-group-adjustable-cheek-riser.html?_iv_code=1S0-SCP-TMGCHKRSR-GSCP
FDE finish on the FAB Defense GL-Shock with a GSPC Cheek Riser and GSPCP Picatinny Rail Adaptor may be similar to the Magpul FDE. However, the exact shade may very between products so I recommend contacting the manufacturer to see if they can give more information on the shade of FDE it is.
As long as you are using a Standard Mil-Spec buffer tube, the FAB Defense GL-Shock with a GSPC Cheek Riser and GSPCP with Picatinny Rail Adaptor will fit fine.
That will depend entirely, on what CA stock pin you have. It should work with most.
The design and buttpad are what helps with the recoil mitigation.
The main difference is going to be the style of cheek riser.
Yes, the mono-pod add-on is specifically designed to be compatible with the GL-shock stock.
Any standard QD sling swivel will work, here is a link to a compatible model:
https://www.opticsplanet.com/magpul-qd-sling-swivel.html