Question on 485 Processing time

[rbtdk]

The link to Processing time shows 485 processing times
anywhere between 400-500days. Will it vary between
category (e.g., EB1/EB2/EB3)?
If someone applied for 485 sometime in Sept.99
when they were current(for EB3 category) with
a priority date of Jan'98, will the 485 processed now
or will it be processed only when the priority date
is moved to Jan'98.

Thanks in advance for the help.