How devs judging legacy bans

Hello, if im steam member since 2014 (so before 2016 november when they did take off legacy)
but i have bought dbd in 2017 (steam purchase history)
do i have an chance to unlock legacy and stay undetected ?
I mean, does devs have opportunity to see when game was bought ? Or they can only know steam account age ?
game buy date is only visible via steam in account settings.
I ask because i could manually edit achievements + legit dates(copy dates, orders from some legit profile). I have 1300hours played so my account would look legit, bought all DLCs legit way etc.
the thing is - are devs also can see when we activated game ? or only steam has power to do it ?

Not going to even read the rest of the question, if your account activation date (dbd purchase date) is AFTER November 2016 you have no way of possibly unlocking Legacy and not getting banned.

And yes, the devs can see when you accepted their Eula, which is technically the first time you launched the game.

Looking at your account activation date is an easy and fast way to tell whether the Legacy is legitimate or not.