HOWEVER: I heard that Emerald is very unstable. I don't know how unstable it is and to what extent.
LOL UNSTABLE.
There is no unstable ROM. Different ROMs have different offsets. This is a common misconception because people don't read. Instead, they use a tool that isn't made for Emerald. Or an inexperienced tool maker uses the same offsets as Ruby because they believe them to be the same. People should at least think about what they are saying before they make a statement like that. Honestly, does anyone believe that Nintendo/Gamefreak would release an unstable game?