I'd say a year old is the oldest. I once met a guy who literally put a photo up of him like 3 stone lighter, it must have been about two/ three years old. I'm glad he did put that photo up in a way; it grabbed my attention then I got to know him and ended up really liking him. it didn't end up well but yeah...
I think it's less about the years and more about how much you resemble the picture. So new hair cut, got your braces off, lost/gained significant weight, change in hair color etc... If you still want a time frame on it, I'll just say within 6 months to a year.
I would say less than 2. And have someone within six months.
As recent as possible. However as always it is subjective. If you haven't changed at all in the last 3 years it seems fair enough to use that.
The idea is to stay (reasonably at least) true to reality. So as a guy, my hair grew a bit thinner and I ended up cutting it all off. 3 years ago I had long wavy thick curly hair. Maybe not the most honest portrayal of my current looks.
I think within a year. Otherwise it feels like you could be lying about your looks. Especially if your a girl who changes there hair a lot. Like your picture can be you with long brown hair when you now have short blonde