Bought this elixir straight from Nykaa. Billing details are attached.
So it's 100 % authentic.
Used it 4-5 times only. You can see from the images only little bit of it is used. However selling it cause I switched to other serums.Also i believe very much in hygiene so no way the dropper has been touched on face. So please be assured about that.

It's quite light weight in texture. You can read the elaborated details about it from google and the images provided.
Don't have the expiration details on it however you can scan the product.