Is it true that all pieces with raised marks are fakes?
I have found two matching pieces with Qing/Quianlong marks that are raised in the porcelain.
These pieces are small vases with dragon faces on opposite sides and the dragon faces have moving eyes and other parts.
These are very complex and I would think would be costly to fake.
There is several questions raised in you mail.
First there are two types of "raised" marks I can think of right now. Colored enamels applied on top of the porcelain glaze make the first type, and those are indeed mostly late. The second type is as you indicate you have found raised in the porcelain itself. They do occur from Qing/Qianlong time but also later and could not be used as the sole criteria for a date.
The second question is what constitutes a "fake". As I see it a fake is anything made and sold as something it isn't and maybe with the intend to deceive. Your vase could quite possibly have been made and sold as a recent piece without this in any way being a fake. The fact that the mark in that case would be from a different period then the piece is very common. In fact it seems to me that most marks are.
To help you with a date, though, I would need at least one picture and preferably also one of the mark.