Considering the reason he remembers is because he saw her topless is chapter 1, I imagine more people actually remember and just pretend they don't notice. Or that explanation was a lie.
He cleared the 100, took the optional visit to 1 previous world before returning to his own, and then used his last skill to reset his whole loop. So he hasn't cleared the challenge.
@Kizuwono The FIRST chapter says he has 6 months to a year without the surgery, and with it he'll have a 30% 5 year survival chance, and no chance of an actual cure.