Some fundamental Blockchain Questions

Hi everyone, I hope I am in the correct subreddit for my questions. I am reading up more and more about Blockchains (currently reading The Token Economy), but there are still many questions popping up in my head and Google search isn't always helpful because there are lots of articles which are not going very deep into the topic. Maybe someone here can help me out with some blockchain fundamentals or point me to the right resources:

1. What's the relation between blockchain and wallet in regards to **what data is stored and managed** by each entity? As I understand, the blockchain keeps track of all transactions while the wallet generates ones private key, public key, and address. If the wallet generates those, how does the blockchain know that there is a new participant in the network? I am guessing the blockchain doesn't know about this participant, until the new participants sends their first transaction to the blockchain. But I am not sure about this.
2. How is the problem of quantum computing taken care of in the example of Ethereum/Ethereum 2.0? If quantum computing becomes a thing, it should get easier for these to decrypt public key from address and private key from public key.
3. If a blockchain stores only transactions, how does the blockchain know how much token every participant in the network holds? Does the wallet with your address aggregate all your historical transactions on the blockchain to the result?
4. A block in a blockchain consists of transactions. If a transaction is made, it's broadcasted to all nodes which verify the transaction. Once there are enough transactions, a block is created. Question(s): Do all nodes in the network start to create this block at the same time? And if so, will they abort their work if one node (the winner) broadcasts its block? What I am wondering here: what's the timeline of these events and for each event what does each node do?
5. Why has a wallet public key and address if both are accessible by others once a first transaction is sent?
6. If a block is hashed upon creation, how do block explorer applications know how to de-hash the block? Is the hash function known and always the same?
   1. Are transactions in a block hashed as well?
7. How is it taken care of that there are no duplicated private keys if the wallets do not know about each other. I know that there must be a function which creates this randomness, but how to guarantee its uniqueness?
8. If a person sends a transaction, as I understand the transaction is send as plaintext and as a hash. Then nodes can hash the plaintext and verify if its the same with the hash. Why sending a hash and a plaintext in the first place? My guess: Making sure of the integrity of the transaction, so that no one tampered with it in between, but I am not 100% sure if this is the reason and/or whether there are other reasons.
9. If one sends a transaction to the blockchain, how do nodes get notified about this? Do they just sync every X seconds with the latest transactions on the network?
   

There are many more questions I need to dig deeper, but I don't want to flood this subreddit and need to do my own research as well. Thanks for your kindness!