Do you mean testing as a different type or generally in life coinciding with a particular type? For me the first did make a difference initially, until I realised that it doesn't matter what type I really test as, its a good indicator, but I should remain myself and not live up to any a personality trait if its not me, if don't want to.
For the second question, I've felt I've changed slowly. I think for a long time I was very INFx, then started living in my shadow, numb abit detached, sometimes due to depression, but now returning to something like INxx, back to normal again now. Initially I was very idealistic I think anyway. Now that have faced myself gone back to INFx.
As you say that the journey of personal identity, never finishes, it continues, in new circumstances, conditions, since the person who you are changes with time.