How Do Peers Choose Which Peer To Trust?

How Do Peers Choose Which Peer To Trust?

1. So the way I understand how the blockchain works is that each new block uses the previous block's hash, which means if my block[100].hash != someone_elses_block[100].hash that means that either I broke some rule, or the other person did; In this case, how does my client find a trusted peer? And WHERE does my client get the latest CORRECT blockchain? Is there a central server for it? If so, where did the server it from? Because the miner will have the longest chain, but what if they are not actually following the rules? Then what?

2. Lets say I stopped my client for 100 days, during those 100 days there was 500 new transactions, which means that if I was to compare my last block with someone elses then my client would be outdated, therefore it needs to download the extra blocks, where does it find these blocks and how does it determine which peers to sync to and to trust?

3. A question about the nonce, if lets say there was no nonce; If client A has a chain that followed the rules and client B was verifying transactions without actually doing all the proper checks, that means that client A at block[100].hash != client B at block[100] therefore client B is not following the rules, so the question is what is the real need for the nonce? Because in my mind it seems like it's just there to make it harder to mine for people, correct? Or does it add some sort of security? And if it does, will it have the same security if let's say the nonce was always any number between 0 and 15? Or would it have to be adjusted as mining gets faster?

Thanks!

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