Questions about the FOTM feature

Hello, I have a few questions about the whole FOTM feature.

  1. How often does the rank update in response to a buff or nerf? Is it a month since it’s called FOTM?

  2. What determines the rank, and do abilities that no player has reached the level for affect it as well?

  3. Is the effect where it seems to favor a certain class as S while others are D tier even though they have similar times to level and die because of low refresh rate, or are my classes uber-unbalanced and I have no idea?

Thank you for your help.