*shrug* I'll let someone else answer the questions, then. Not into Gens (sic?) myself or I would have answered the questions in the same post.
All I'm saying is that you're asking questions about Genesis emulators in a forum about bulding faux arcade machines. The two really don't go together, there are plenty of better message boards for these kinds of questions (esp. when they are emulator-specific).
But, off the top of my head:
- Can i rename the extensions of the gens roms to .smd?
More than likely. Just try it, the extension should likely always be .bin or .smd for Genesis roms (as far as I can remember from the Genecyst days).
- Are they updated frequently?
What is 'they'? The emulator? No idea.
- Is gens 2.11 the best emu to run them?
No idea; but with console emulators, you usually have to get several and play the games that work in the emulators they work in.
- Will a arcade vga make them more authentic!? Like tv aspect?
Computer monitors aren't the same aspect ratio as TVs? Genesis was originally made for TVs and I believe CGA monitors are actually a slightly lower resolution, so I'll gamble and guess no.
- Some roms when i'm playing them at gens are 'resized' constantly, is it a rom problem or emulator?
Most Genesis emulators seem to do this. Different screens will have different resolutions, it seems.
- When i push the horn in micromachines (all series) it sounds weird, doesn't sound like the cartige sound! Is it a emulator problem or the rom is deprecated?
Sounds like an emulator problem. To be [somewhat] sure, try another emulator.