Of course the first two things do sometimes happen to people. But people in a psychotic state very frequently think they're happening when they actually aren't happening. A high percentage of them believe it, but out of that sample, the belief is almost never actually based in reality.
That's why I listed a myriad of symptoms. If someone solely believes that, say, some people are following them, that's one thing. But if someone thinks people are following them and that some entity is implanting thoughts into their head via futuristic technology, then they're very likely in a state of psychosis.
If you haven't committed any crimes or done anything noteworthy, it's especially unlikely any government is going to devote resources to following you. If you know you've committed some serious crimes, then it's certainly a much more rational fear and could be real.
Also, if you're really being followed by a government IRL, odds are you're not going to notice it unless they want you to notice it, and that pretty much doesn't happen unless you're an important figure traveling to a foreign country and they want to intimidate you. It's not impossible that you could notice it, but when multiplied by all of the other probabilities, it's very unlikely. Especially if you hold other paranoid beliefs.
>Who decides what's real? Is it not real unless you've got audio?
If you hear someone talking to you but you don't see anyone nearby, or if you hear something/someone while no one else near you hears anything. But, yes, if you try to record it and don't hear anything on the recording, then that would also be an indication.