Difference between 现在几岁 and 今年几岁
现在几岁 sounds really weird. People usually say 今年几岁 or just 几岁 to mean the age as of right now. Come to think of it, I think this might be because there's a different notation of age which increases every lunar new year.
Edit: as pointed out by the comments below, 现在几岁 doesn't sound really weird in general. It's definitely less common than 今年几岁, but maybe it sounding really weird to me is a dialect thing.