Is it possible for symptoms to go away and come back? Or get better then worse and vice-versa?

The normal progression of ALS is that once you lose some function (hand, arm, leg etc) to ALS- it doesn't return or get any better. ALS is progressive.
Now it is possible to have worse twitching on one day than another- but as far as if your fingers on one hand get to where you can't use them, then you won't be able to use them a few weeks from now.
Hope this answers your question.