Sans gets a little memory from non-true resets, but literally every other major character does. The only difference is Sans is AWARE ABOUT EXISTENCE OF RESETS and of course he'll give those pieces of memory more importance. But that still doesn't mean he remembers literally everything.

Is Papyrus aware of the resets?

Sans and Papyrus seem to be aware of resets. Fandom. Sans and Papyrus seem to be aware of resets.

Does sans remember if you kill Papyrus?

Because Sans is dying, he doesn't remember Papyrus is dead, so if Papyrus came back or Sans hallucinated, he isn't like "Papyrus, weren't you dead?".