As far as I'm aware 1.1 is the go-to tfs. I'm unsure if it is the most stable, but most people seem to be migrating over to it.
(I work with someone who has invested months/years into a 0.3.7 tfs, so I don't know much more then that.)
As far as scripts are concerned 8.6/10.77 have nothing related to scripts, unless there are pre-programmed aspects of the client that can be used.
0.2xxx/0.3.6xx/0.3.7xx/0.4xx/1.0xx/1.1x (x meaning different possible revamps or versions/updates) are the main scripting points.
I'm unsure how to clarify, but if your ever needing help with a script, telling people your client version is completely useless information. (8.6/10.77)
The main different between older script 0.3.6, and newer 1.1 seems to be how it was scripted.
Basically to call the same function requires slightly different code, as it was scripted by two different teams.
I really can't explain better as I'm not really the best person to ask, and I don't know enough to make an informed reply.
But 1.0 was the initial release and 1.1 is 1.0 with bug fixes, and changes still happening. Idk if there is a 1.2 yet, or if that's the planned final release.