1. You should probably use the current one for modeling, but 2.49 for exporting.
2. The blender website should have some tutorials for texturing, if not I'm sure you can find a guide somewhere.
3. No idea (Mainly don't want to take the time to learn about subtracting :C)
4. Not sure again, But there are ways you can model things to get them symmetrical without it. (Eyeballing it is always good too,but if you want to be perfect)