1. He is dismissive of them/He is sceptical about them.
2. He became suspicious when he started seeing online adverts for something he had bought the day before, even though he had not searched for the product online.
3. i) NG
4. If they've never experienced it, they prefer to deny or ignore that it might be happening.
6. It refers to Facebook. It is allowed to listen in on conversations through users’ phones.
7. We might suddenly notice an advert because we've thought about it recently, when it’s actually been in the background the whole time.
8. He is suggesting that the authorities don’t actually spy on people, they just want to cause fear and suspicion to distract them.