1 - As far as I am aware, you can’t do a take off at 125m without the RVR working, so the lowest vis is 150m for take off, therefore you need to see 10 lights at 15m spacing.
2 - one RVR can be missing, therefore you can make the approach, if you can see what you need to see, land, if you can’t see what you need to,go around.