How do you reformat an R4ds

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)