The events of Persona 1 and 2 happen within a world separate from the events of Persona 3 and 4, so characters from 1/2 canon will need to arrive in Inaba on the train along with the rest who come from worlds not native to P3/4 (and thus Caligo) canon. However, since they are characters who already possess a Persona or Personae, their abilities will not be sealed in the same way and will simply be transferred over along with them. We're not entirely sure what you mean by aging, then, since you'll be able to pull your character from anywhere within the canon's timeline due to it being a separate world.
The knowledge of how to utilize potions and such wouldn't be touched. However, the materials necessary for such things may not show themselves right away, and the character would need to have a working knowledge of how to create such things. Such a thing wouldn't be plausible right away, as we mods would like to work out the specifics on that sort of a thing before we allow it outright. In the meantime, it might be best to think of it as a dormant ability.
no subject
The knowledge of how to utilize potions and such wouldn't be touched. However, the materials necessary for such things may not show themselves right away, and the character would need to have a working knowledge of how to create such things. Such a thing wouldn't be plausible right away, as we mods would like to work out the specifics on that sort of a thing before we allow it outright. In the meantime, it might be best to think of it as a dormant ability.