Pick a power: Slow down time or Speed it up.

Check yourself before you wreck yourself. Which, in this case, you already did, so I don't know where we go from here.



2013: I am 20 years old. I slow down time 0.1x (10 hours for me = 1 hour for everyone else). I live in that speed for 10 years.

2014: I am 21 years old. I have lived for 10 years under 0.1x speed, but because my body ages in normal speed, I am only 21.

You metabolism is not changed for those 10 years, you have aged 10 years while real time has only progressed through 1 year. Everything outside of yourself slows down, you remain unchanged. 2014, you are 31 years old. The only way to reach your conclusion is if your body aged in slow speed, not your bolded, normal speed, which is, against the rule.