Sunday Riley Luna Sleeping night oil 0.5oz15ml

Q: Should it be used as the only one skin care at night? No moisturizer is needed afterwards?

it completely depends on what your skin type is. I have extremely dry & sensitive skin, so for me I use this and a 5% retinol (I worked up to 5% slowly starting with The Ordinary .5% retinol and whet from there) and a very heavy duty night creme moisturizer and the Luna sleeping oli as well.

Q: how is this different from the Sunday Riley A+ high dose anti aging retinol serum?

A+ is a pro-level formula for all skin types. This pro-strength formula is designed for those who want "serious results without serious downtime." Luna is an entry level formula for all skin types. Our original trans-retinol acid ester was created for those who are new to retinoids, while also keeping sensitive skin in mind.

Q: Why is tgis product so much cheaper on Amazon than in the stores? Has it been tampered with or replaced with something else?

It isn't cheaper. There are 2 size options, both of which are the same price here as on the Sunday Riley website. Also this is the official Sunday Riley seller here on Amazon.