the question is a bit vague:
The best model for R4DS: The original R4DS (not pro, not ultra, not SDHC, not R4i etc.)
The best kernel version: v1.18 (Released 24th April 2008)
www.r4ds.cn
March.
1.18 is the final official release for the R4DS, so that is the firmware version that most people would use.
huh? the R4DS is for the Nintendo DS.
no, but there is no need to, the R4DS has a built in Action Replay.
You can go to the official R4DS site and download their latest version, which should be v1.18. Delete everything in your R4 and just copy everything in the .zip file and paste it in the microSD card for your R4DS.Download v1.18: http://www.r4ds.cn/download/r4_v1.18_kernel.html (It's at the bottom of the page)
No it is illegal
Yes the r4ds boots up game boy games into ds mode.
no it is not illegal
no
The official R4DS comes with a CD with everything you need on it. Unofficial ones do not come with a CD, so you will need to find out which website you need to go to for the downloads. You can check the website from any packaging your R4DS came with.
r4ds.cn
NO !!!!!!!!!!!!!!!