RE: Where opera-mini 3.2 disappeared?
Yes, heap memory is the kind of memory that Opera Mini can use on your phone. That kind of information (heap size) is very hard to find... as I wrote before the Nokia page was very good before Microsoft time. Most manufactures spec pages do not show heap memory.
And yes again, there is a difference between 3.2 and 4.5. 3.2 took about 100 kb installed on phone and 4.5 takes about 200. That is what we have to pay to have a modern browser running. 4.5 contains a lot of features that consumes more memory.
A phone with 30 MB internal and 3 MB heap is very suited to run Opera Mini 4.5 but (I have to say but!) it also depends on if it is a touch screen phone or not. And of course the size of the screen is part of it as well. That kind of phone should also be able to run Opera Mini 8 but I prefer Opera Mini 4.5 :).
It isn´t that easy to say if Opera Mini 4.5 / 8.0 will run fine on a certain phone just by looking at memory available. The implementation of java is quite different depending on brand.