Please don't report three issues under one ticket, unless they are so closely related that they cannot be separated.

I don't understand what your second issue actually is. You refer to the docs that specify extended syntax as [start:stop:step] but then you tried [start:stop,step] which is correctly an error. (Notice the comma instead of colon.)

And again, your third issue to do with list.insert ... what is your actual bug report? Have you found an example where these aren't equivalent?

alist.insert(pos, value)

alist[pos:pos] = [value]

I don't understand your third bug report here... you show two examples where the insert function works as documented. You say you didn't expect the behaviour, but what behaviour did you expect?