Flowey in Underground was the first, Frisk second. ... Flowey remembers your resets because he had enough determination at one point to reset himself.

Does Flowey remember true resets?

It doesn't remember anything, actually none of the characters remembers, you can erase 99% of what you did after the true reset.

Who can remember resets in Undertale?

There has been so many fan-fictioners/normal fans out there that think Sans can remember True Resets, or normal resets like Frisk. Let me explain, Sans CANNOT remember it all- just slightly remembers- but the other things he said that makes the fans think that Sans can remember the reset all, nope.