Hello! Without doing a lot of research into Exalted, which we can't do for questions about hypothetical apps, we can only provide some general answers.
Necromancy in Thedas generally involves putting spirits into corpses, and not necessarily spirits that match those corpses. Whether the dead have a soul or leave traditional ghosts is unclear; there definitely are spirity beings that take on the forms and personalities of the dead, but these generally seem to be spirits, as separate entities, who are echoing what they saw of the dead while they were living, rather than some actual piece of the dead person themselves. In FR we would not allow anyone to actually bring someone back from the dead, but we do allow people to use abilities that allow them to speak to the dead and so on, though usually on a limited basis and with the background understanding that it's these mimicking spirits rather than truly the dead person speaking.
Whether your character could reproduce a tonic and so on from their home world would depend on the specific tonic/potion and what it could do. We won't be able to go through a list and say yes or no to each one prior to receiving an actual app, since we nerf holistically to balance rifters' overall power sets and whether certain unique alchemical solutions are allowed would be based in part on how powerful their other abilities are. However, someone who is generally skilled with the mechanics of alchemy could likely eventually learn native recipes for native potions with time and study.
For integrating canon sources, we would generally ask that you choose one to be you main source and use others only to supplement holes in it as necessary—so, for example, if you choose the 3rd Edition, you can add information from others where those others don't contradict the 3rd, as long as it all makes sense together and fleshes out the version you chose. To the extent that the versions contain contradictory information, you would need to pick one as the version that "trumps" the others and stick with its version of the canon for all aspects of your app rather than picking and choosing facts from multiple versions.
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Necromancy in Thedas generally involves putting spirits into corpses, and not necessarily spirits that match those corpses. Whether the dead have a soul or leave traditional ghosts is unclear; there definitely are spirity beings that take on the forms and personalities of the dead, but these generally seem to be spirits, as separate entities, who are echoing what they saw of the dead while they were living, rather than some actual piece of the dead person themselves. In FR we would not allow anyone to actually bring someone back from the dead, but we do allow people to use abilities that allow them to speak to the dead and so on, though usually on a limited basis and with the background understanding that it's these mimicking spirits rather than truly the dead person speaking.
Whether your character could reproduce a tonic and so on from their home world would depend on the specific tonic/potion and what it could do. We won't be able to go through a list and say yes or no to each one prior to receiving an actual app, since we nerf holistically to balance rifters' overall power sets and whether certain unique alchemical solutions are allowed would be based in part on how powerful their other abilities are. However, someone who is generally skilled with the mechanics of alchemy could likely eventually learn native recipes for native potions with time and study.
For integrating canon sources, we would generally ask that you choose one to be you main source and use others only to supplement holes in it as necessary—so, for example, if you choose the 3rd Edition, you can add information from others where those others don't contradict the 3rd, as long as it all makes sense together and fleshes out the version you chose. To the extent that the versions contain contradictory information, you would need to pick one as the version that "trumps" the others and stick with its version of the canon for all aspects of your app rather than picking and choosing facts from multiple versions.