Alicornutopia

So summonees can carry rewards of live animals like cetaceans and apes to the afterlives? What happens if they try bringing humans?

Humans cannot accompany them.

Anything happen if you try to carry a highly advanced computer system such as Jarvis?

AIs on sufficiently portable hardware could go back to daeva worlds with daeva.

What happens if a Jarvis makes a summoning circle from within a daeva world?

Hmmm... I think nothing. I think you can't summon from within daeva worlds. (Normally, for non-sandbox purposes, you can only summon in the single relevant mortal world.)

Ooh, and they could bring ansible-halfs if anybody invented one and told demons about it.

I am a bit disappointed with demon culture for not inventing standards for an Internet even after the mortal world did. Presumably they at least standardized their EM spectrum a bit; that's a common resource that needs standards for anything wireless (like Cam’s brain chip) to work in cities.

Could daeva develop self-concepts and the associated indestructibility on detached things, or must their bodies be contiguous at all times? Does the same allowance for self-modification extend to Limboites, even if they don’t have as much practical use?

...Now that I've thought of it, I'm really interested in the interaction between daeva self-stuff and Unbitwise's claimverse's claimed-stuff.

Claimverse's* opinion on the matter is that if it comes up, daeva selves should resist claiming by others in exactly the same way as someone who claimed their own body and was trying to resist would. If the daeva does the “decline to consider it part of themselves” thing, then it's no harder than any other biological matter (that is to say, quite hard).

* The universe declines to have an official name until someone ICly names it or I work out enough conlang to get one that way.

Could a daeva consider kortarem part of themselves?