For MRS lounge, not sure but you can try. In case it doesn’t work, you won’t miss a lot. And MRS hall 3/4 is rather pleasant for waiting as there is a nice view on the apron and a lot of natural light.
For CDG, as said by Xandrios, you will likely leave from K (99%). Just go to K lounge don’t bother hopping around. You can register to the Clarins spa when you arrive in the lounge. But slots are taken quickly, so do it as soon as you arrive in the lounge.