Nothing about a cosmetic can be verified from a description, which makes this a category of showing rather than telling.
The questions
"Can you show the seal?" Intact, on camera. Non-answer: a photo of the front of the box.
"Can you show the batch code and the dates?" Close enough to read. Expiry or best-before, and the small open-jar symbol with a number and an M, which says how long it is meant to last once opened.
"Where did you buy it?" That is the only provenance a cosmetic has, and counterfeiters target this category hard.
"Has it been opened, when, and how much is left?" A percentage and a photograph where the container allows.
"Is the carton included?" The codes and dates live on it.
Two things to refuse outright
Anything decanted or repackaged. If it is not in its own container, do not bid.
Anything sold with a claim that it treats or cures something. That is a claim nobody can support, and medicines and supplements need a licence the seller must hold. Prohibited items.
What protection covers
A product unsealed when described as sealed, past its date, or visibly different from the one shown: seven days from delivery.
Questions people ask
What does 12M in the jar symbol mean?
Twelve months of intended use after opening — starting when it was opened, not when you receive it.
Is a product past best-before unusable?
Not necessarily, and it must be declared. Decide with the date in front of you.
Should I buy used makeup?
Some do, many will not. Only where the seller says plainly when it was opened and how much is left.