is this one good for acne scars

This is a predominantly moisturizing mask so, short answer: no. Long answer: it is here for the long-game of fighting wrinkles and keeping your skin fresh looking during winter months or in dry climates. To decrease the visibility of acne scarring, look for ingredients like hydroxy acids or lactic acids. Most over the counter masks will not completely improve severe scarring other than in-office procedures performed by a professional dermatologists or prescription cremes, but daily application of acids are a good option in lieu of flash treatment with a strong mask that may leave your skin red and reactive.

where in your routine does this go? before or after cleansing? I get that it must be rinsed off, but to you cleanse properly before?

Use it after you cleanse your skin. After you use, the mask, moisturizer regularly. However, it's a mask so it's not something you would use everyday. I use it about 3x a week. Makes my skin feel so refreshed after!