A:AnswerYes, I just returned from Germany and it worked perfectly to track my items. I was also able to track my items in The States while traveling overseas.
A:AnswerYou can set up Find My so that you receive a notification if an item is left behind. I think you have to be out of bluetooth range to receive it.
A:AnswerI think there's a quite a few assumptions in this scenario. I think its primary purpose is to track your IOS devices in the event of loss. Yes, if a person had nefarious plans, and stole your backup lets say, then yes it would appear on their iPhone. They'd have to find the airtag and then disable it. But there was just a story in the news where this happen and the owner still had their last location and gave it to the Police..By "Access to the tracker" I think you mean can the control it. The answer is no. They could however in theory, take out the battery, reset it, and use their IOS devices to make it "theres".