Yes, just checked for features of the phone online, it's 1.5GB of RAM.
Also finally checked the developer section's RAM overview:
"Opera for Android" has 4 entries while having 18 tabs "open", "Opera Mini" has just one entry while having 33 tabs "open".
Apparently, CPU Info's "available" space/RAM isn't really "free" RAM as the developer's sections RAM view shows some 65MB of free RAM while CPU Info about 400MB "available"... On the other hand, in the developer's sections there are two view options, "processes in cache" and "active services". With the latter the free RAM value matches the value of CPU Info.
With "processes in cache" the opera instances are shown and shows a lower value for free RAM.
On both versions of Opera data saving is activated.
So, the limited RAM seems to lead to "Opera for Android" to have to auto-reload the pages. I just thought it was a "feature" as a few versions back opera finally made it optional to have a new tab opened automatically after a certain amount of time of idle (or something along these lines...)...