The lakes i fish don’t have shad in them. Will a bass still bite on a shad swim bait, if they aren’t use to seeing any shad around?

Probably. I use trout swimbaits in waters that have No trout, yet still catch bass. I doubt shad would be different.

Yes. 

Yes, I rarely see worms swimming around in the lake but bass will eat them!  Movement and shape allow for instinct to set in and EAT whatever they want.  A shad profile would be no different.   

Yes they will.

A shad swim bait or shad colors still matches a lot of other bait fish, like shiners, white perch, chubs, suckers And fall fish.   A shad shape , matches a sunfish and shiners , while the color matches the other species I mentioned 

I’ve seen a few swim baits in bass pattern along with the others you guys have mentioned. Pretty impressive realistic patterns on them. Big bass eating smaller bass. Happens quite often I’d suspect?

Bass are bullies....they intimidate and eat everything to include their own! Ive caught bass with all kinds of things in their gullet. They do no discriminate!

They do get keyed in on abundant forage. In a lake with no shad, probably bluegill would be the most prolific fish in a pond/lake.