EDI is the PS2, Catalyst A.I is the IPhone. Do you see my point now? Technology is bound to improve and for a being that has been alive for as long as the Catalyst A.I. is it really reasonable to make the assumptions you make?
You managed just to confuse me more. I am not the smartest guy in the world, so explain your ideas to me. 
How big is the Catalyst A.I.'s processor? Why would it need to be retrieved? Why would it want to jump into the extranet? Why would the backup data be tied to him? Why would the Catalyst decide to stay in the same Galaxy? Why would it not replicate itself? Why would his replications not be active? How would you know if they were? Is the Catalyst truly the first A.I. or just a copy?
I explained why I think the Catalyst A.I. has a back up, not only because it is smart. But more specifically it is smarter than Mass Effect humans, protheans etc. If Bioware wants him in Andromeda he will be there.
First things first: The Catalyst is as dumb as a brick. He really is. This problem he searched a solution for was nonexistent until the moment he rebelled. His solution was utter crap and his whining about "synthesis cannot be forced" is a joke if you think about it. 
Ok let´s say his hardware needs are not important for the debate as we don´t know if it runs on nanoscale computers or has the biggest cupboard of computer hardware ever seen.
I think that there is no backup because it didn´t went online the moment the Crucible docked and the catalyst thought "I let this human in here, explain to him where the off switch is and raise a platform so he can walk there" instead of simply letting Shepard bleed out on the floor below. In the low EMS ending there is only destroy by the way. This would be the moment you need a backup for.
And well every backup connected at the moment of Shepard´s decision would probably be affected by the decision. Eventual backups are probably on Sovereign class Reapers anyways. I mean can you find a better place than a highly mobile battleship able to take a lot of damage and dish out a lot of pain? You don´t have to put it on the front lines if you are concerned that the primitives can shoot it down.
This leaves unconnected backups hidden away. Backups and updates of the backups are probably done via some internal Reaper network or so. In the destroy or the control ending there is nothing left of the network or another AI is now boss and I am pretty sure that Shepalyst wouldn´t like the competition. It can´t upload itself on other channels because the Reapers took potshots at the buoys to cut off communication.
So yeah there is no one left and the backup entity is left stranded somewhere unless Bioware does an asspull and says that he has his own craft that isn´t affected because of reasons.
Why should it replicate itself? It´s not his purpose, reproduction is an organic thing. His purpose is to achieve eternal peace between organics and synthetics or the reapers give him purpose, whatever his deranged processors are up to.
Why didn´t it go to Andromeda besides Bioware being smart enough to realize that only a tiny minority would want the Reapers again and that starkid is probably one of the most hated NPCs in the franchise? Well, why should it go to Andromeda? And until Bioware reveals how the Ark project goes to Andromeda, we don´t know how it was possible to go there in the first place. It could be that even Reaper drives break down after a hundred years at full speed and the only way to cross conventionally would be to slow down to one light year a day.