Re: taste- I don't know as mine hasn't returned yet. Professional opinions range from one month (my RO) to one year (my ENT). I think it's safe to say they don't know either. My goal is to get enough 'nutrition' every day to make it to the next day, etc. Eventually the day will come when I'm able to eat 'normally' again. In the meantime, I'm slowly losing weight.
About 3 months after the end of treatment seems to be the consensus for the PETscan.