Yes, and yes.
WCB6200Q and G1100 can be unlinked to G3100 using Ethernet. Furthermore, G1100 can be uplinked to G3100 using coax. Verizon version of the WCB6200Q cannot be uplinked to G3100 using coax, however, Actiontec NCS version of the WCB6200 can be uplinked to G3100 using coax. Regarding the purchase of WCB6200Q, if you have to buy one, please buy the Actiontec NCS version to avoid MoCA compatibility issues (and also cheaper).
To convert G1100 into an extender, please follow my interactive widget located to the right of the Forum. https://forums.verizon.com/t5/G1100-Bridging-Guide/bd-p/g1100-bridging-guide