Well, the three questions are pretty much the same one
The idea is that you should be able to develop your games in your PC (windows, linux, whatever) and then port your games without much trouble to the Wii, as long as you've followed a few rules when developing them in your computer. You can find the details here:http://code.google.com/p/bennugd-monolithic/wiki/WiiGettingStarted
But they're, basically:
DCBs created in your computer won't work in your Wii -> to play your games in your Wii, you have to compile them in your Wii [howto
Your game resolution should be 640x480.
16 bits color is -obviously- faster.
You have to recode your songs to 48KHz (In your computer they're typically 22 or 44KHz) for them to play at right speed. If you want to avoid problems, you can use module tracker formats (XM, S3M, IT...) for the music.
To be able to read "advanced" data from your Wiimotes like orientation, accelerations... you have to use mod_wpad. You can find its documentation in the wiki and instructions on how to make code that uses mod_wpad and compiles fine in both your Wii and your PC here
So, basically the idea is that it's easier to make your games in your computer and from time to time test them in your Wii to make sure that everything is working as expected.