1) Not sure
2) I would assume they all came out around the same time. One after the other closely together, but that's an assumption
3) 1st gen, had a couple of problems. 2nd gen was mainly to fix those problems I believe, they may have made some other small changes as well, dunno. 3rd gen got a new trigger (SA/DA) and new sights, prolly a couple more 'fixes' from the 2nd gen.
4) Taurus is known for taking other guns and redesigning them slightly making needed or welcomed changes. They will share a lot of similarities between other guns sometimes, but are usually better than the original. That may explain the similarities, but I wouldn't think KelTech would be one they would copy off of. That very could have been the other way around. I don;t know.
5) The current ones are SA/DA (SA with a second strike feature).
6) I know Qwiks Draw has both. You may hit him up or wait until he chimes in.
7) I believe the 3rd gens come with the rail.
8 ) I have one, but haven't put it on. It's not that bad really. I did sand the checkered grips down some to make it a little easier on the hands. Other than that, I haven't had any problems or complaints with the recoil.
9) Mine will cycle HydraShok low recoil (165grain) and Aguila IQ with no probs.
10) I would like to have one for the guide rod, but have come up dry so far. You have to watch accesories for the MilPro's cause the rail is so short and it will hit the trigger gaurd if it's not short enough. That's the only problem with the gun and rail accesories.