If I purchase an item on Amazon can I get that item engraved

Not by Apple. Apple only engraves items purchased from their online store directly. The engraved option is only available during checkout at Apple Online.

You could take it to a third party engraver, but it may void your warranty.

Engraved by Apple, I doubt it. As far as I know, Apple only offer to engrave devices purchased from them.

The fiend is saying right. Is it possible to put all the item responsibility to your digital marketing agency?