Hi , if I take out the battery of a airtag will anyone know that I took it out ? Like the person who owns it ?

No ... because, the AirTag will no longer show up in Find My. It's last known location may appear for up to 24 hours after it last reported to Find My.

Basically, yes. An AirTag is associated with the owner's Apple ID. When the battery is placed back in, and the AirTag has not been reset, it would still be associated to that ID.

Well, if you take the battery out the owner will eventually realize it is not functioning. So yes, they will know.

Bottom line, if your goal is to avoid being tracked without the owner of the AirTag knowing it, the answer is no, they will know you tampered with it. Is the owner a parent?