What does 而在此前 mean?
而在此前 means "Before this".

In this context, that means before this date (2017年11月15日) or before this rule became effective.



而 = 然而 (conjunction 連詞)
在 = at / on / in (preposition 前置介詞)
此 = this (this date / this rule became effective)
前 = before



This phrase can be expanded to:


  然而，在此之前