Answer to question two is yes for Bitcoin and all blockchain like that. There are some new ones like Mina who propose a different system in which you only need to verify the last hash.
Answer to question three is not restricted to Bitcoin. There are many other systems, e.g. Proof of stake (POS).
You got them all wrong. I wasn’t talking about bitcoin specifically but about cryptocurrencies in general. If you’re interested in learning I can help but not with that attitude.