1) What you said, plus e.g. no reflection so no serialization or RMI.
2) Nokia's devices for example are pretty much all 12-bit colour nowadays (4 bits each for R,G,B), and come in three main resolutions: 96x65 (e.g. Nokia 3510i: low-end but high volume), 128x128 (e.g. Nokia 7210, 5100, 6100, 3300, ....) and 176x208 (e.g. Nokia 3650: the 'Series-60' camera phones).
3) I can recommend the tutorials and examples at forum.nokia.com (but then I would, I wrote several of them
4) Basically don't bother trying 'real' 3-D yet, unless you go the Symbian C++ route with those Series-60 devices. With MIDP Java think more along the lines of e.g. Game Boy Color capabilities, with an additional restriction that everything (compiled code, sounds, images, ...) has to fit into a typically max 64KB JAR file, but the additional advantage of networking capabilities. Longer-term, the JSR-184 Mobile 3-D API
demos at JavaOne looked promising.