Root can change its identity. Like it will show other imei number, model number, specs (if you check on any app) etc.
Bro, if you got replica, then you have very weak used phones buying skills, so best get official warranty phones.
Replicas are very easy to spot.
Checking imei online helps a lot. Most of them get caught at IMEI verification.
It depends on model, but there are certain things to do in different brands,
Researching online about clones vs original. YouTube helps.
Thorough visual inspection and thoroughly trying live demo units.
Comparing with an original piece, like you could have checked J7 live demo units and then you would have known straightaway that clone J7 you are getting has noticeably lower quality display, performance and camera quality etc. Replicas are noticeably different (weaker) in everything, even in software. So its easier to spot replica once you are familiar with original models.
In Samsung
Boot into download mode to check exact model number and dialling #0# and testing everything in the menu helps a lot. Most of the replicas get caught in this.