95. 97. 98.
By reset we mean he never talks about the past or past pokemon and he also doesnt age :P
He still does, though. xD
In the third episode of AG, Ash had memories of Misty and Brock, and told May and Max that Brock used to cook for the two of them. Plus, Max also recognized Ash as one of the top 8 of the Johto League, which Ash acknowledged. And of course he remembers his Pokémon too! After May caught her Bulbasaur, Ash remembered his own Bulbasaur and even brought it back from Oak, just so it could meet up with May's Bulbasaur. And a lot of his Pokémon come back throughout AG as well, most notably after the Hoenn League ended, and during various instances of the Battle Frontier.
As for DP, there weren't as many references to the past, but Aipom from AG followed him to Sinnoh, and he brought back a bunch of his old Pokémon for the Sinnoh League. Even in BW, Ash remembers the times he spent in Sinnoh when Dawn joins the group, and later during the "Episode N" season, he remembers his Charizard and proceeds brings it back to him (with remastered flashbacks and everything)!
And XY isn't close to finishing, so there aren't too many references yet, but they still exist. During the aquarium episode (XY022), Ash sees a Piplup and says "the one I knew tended to get carried away, though," which can only be referring to Dawn's Piplup. In addition, Ash was already with Pansy at the beginning of the series, since she came with him at the end of BW. When they parted ways, Ash said "thank you for everything up until now," which basically implies he was referring to the past. xD
As for aging, it's not that he
can't age - it's just that his age was retconned to being 10 again in BW, for the sake of simplifying things to present to a new audience. I say "retcon" because while his age was never directly confirmed in AG or DP, you can calculate his age by counting every single day that passed throughout the series. Of course, doing that would be completely impractical, so they just "overrode" that information with a simple retcon. And while it is true that they could've retconned him to be older, that was their own choice to make him 10.
By the way, I finally found that post which I was too lazy to dig up! :D It basically elaborates on why the writers decided to reset Ash's character.
https://www.pokecommunity.com/posts/8726278
