Would like to know some honest reviews from people who not did get the item in exchange for an honest review

This product really works! Tried Garnier first and it did not. I did not receive this for free nor at a discount and my dark spots are fading and my skin looks more brighter and even. I use it in the morning under my moisturiser and got the Retinol same company for at night under my moisturiser. I'm also sceptical about all the reviews on discount or free products. Hope this helps!

does the ingredient: soluble collagen come from fetal cells or any other ingredient come from fetal cells in any way?

The soluble collagen in this product is from a soy complex: http://www.advancedclinicals.com/premium/advanced-clinicals-collagen-instant-plumping-serum

The ingredient list for this doesnt have vitamin c listed (not even under its medical name) any idea if there is actually any in here?

I have checked the box for the ingredients listed, and while some answers have said that there is Vitamin C in this, I do not see anything listed in the ingredients except 'citric acid', and it is listed way down, 6th or 7th from the last. One answer states that Aminopropyl Ascorbyl Phosphate is the 2nd ingredient, it is NOT. It may be the 2nd ingredient in one of the other Advanced Clinicals products, but the 2nd ingredient on the Dark Circle Serum is listed as glycerin.

How does this product compare with their instant plumping collagen serum or the retinol serum? I love the collagen one and am tempted to try the other

The collagen serum leaves the skin as silk, the hyaluronic fills the fine wrinkles (you will notice the change), retinol is applied only at night and has a peeling effect, Vitamin C can be used at night or in the morning and has a tensor effect. Retinol and vitamin C make skin very clear, minimize dark sun spots or age and freckles. I also use the Advanced Clinicals Luxury Pure Argan Oil, because I have very dry skin and this product is excellent, I use it at night. I use all of them for example: two weeks one product in the morning and another in the evening, then the next two weeks the combination of two others, so I see the results. I love these products, they greatly improved the appearance of my face, made it more tense and luminous. I hope that my answer has been useful to you.