Hello Valerio
Glad to hear I have been of help!! Now concerning your questions in your post, I’m not clear on your topology, so I may not be able to answer all your questions.
Concerning the RR, it is possible to configure a backup route reflector so that if one goes down, the other will be able to take over. You can do this by simply creating a second RR, and have BGP clients become neighbors with both RRs. Each one will have a different cluster-ID and will form relationships with its clients. Then you can connect the two RRs by simply making them iBGP peers, or by making them clients of each other.
You could use an ASA in this role as the ASA does support BGP. However, it may be that it doesn’t support the route reflector feature. For example, I have an ASA 5506 running 9.8(2) and it does run BGP but does not have the command to act as an RR. You’ll have to investigate which ASA does include that feature.
As for which model to recommend, I’d need a little more information about your topology and your network requirements including the role that this particular device will play as well as the services that will be running on your network.
If you can give us some more info about these topics, I’ll be able to respond more appropriately to the rest of your questions as well…
I hope this has been helpful!
Laz