Navmap can show inaccesibble/oorp systems. In this regard, questions arose:
1) Which of them inRP and which ooRP? For example, Dauphine has no connections, but Nagano and Alberta connect with Omicron Alpha (consistency of such connection is of course also questionable).
2) Bases that are transferred from old systems (or just from another system) - is it always a retcon or is there some kind of "process" of transferring the base (RP, for example using base constaction platforms or something like that)?
1) As far as I know, all systems that are one side connected are non-existent inRP. Uncharteds are exception of this but they have to be connected by admins for event purpose. Dauphine, Nagano, Alberta, and other, thus, non-existent. Still yet, you better wait for an administrator to answer this, though.
2) From case to case. Dauphine's merge into Languedoc was rather retcon, however, when Maine (old Gallic system) was removed it was done through story of its main star going supernova. Same was when Omega-11 was removed (probably some mentions of its collapse still laying here and there)
Alberta, at least, is probably still an inRP system, considering we had events specifically about its evacuation. Any kind of access is gone, but it still exists out there, somewhere, and can be mentioned in roleplay.
I would like to clarify on the first part: if I get into this system using a jump drive, can I do there some things in RP? I would like to know the administrator's answer.
It's a case by case basis because as mentioned above, some systems were cut out of the game in a lore-friendly way while others are now by-lore part of other systems or were completely retconned, so while there are some exceptions, as a general rule of thumb and for the sake of simplicity, jump-only systems are not considered canon anymore unless specifically stated otherwise. They might be available for strictly gameplay purposes, or might get cycled in and out of roleplay use on event-specific instances, so if you blindjump into an otherwise-inaccessible system outside of any special event, it's mostly just there for sightseeing (or honestly, might just be an oversight, since we generally disable jump for cut systems even if their assets are still left in the gamefiles).