1. Your plan sounds fine. You can do a full, then a differential and restore it fine. Unless there is a technical reason, it might be easier if you took a full backup right before, so then you only have to restore that one image and it would be a little faster. Again, it doesn't really matter.
2. Yes, if you want to rollback you would just restore the full and differential on the computer. I only do fulls, but I believe you select the Differential image first...the manual (or someone on the forum) can help you.
3. "Do I need R-drive Image on the key or not" - Not sure what you mean here. In general, to restore an image, you boot from the CD/USB then browse to and restore the image. Not sure if this is what you mean?