Passphrase & Ledger Nano Queries

I joined the Academy partly because I could learn how to be sure I was buying and storing my Bitcoin in a secure manner. Sadly I have been swamped with work and not able to find time to research some specific questions so I am trying to short circuit this bit of the learning by asking here.
I bought Bitcoin awhile back and setup a Copay wallet to receive it into. I wrote down the 12 word passphrase at the time and crossed my fingers and hoped I had captured them correctly. I have since lost the password to access the Copay wallet in order to transfer the Bitcoin.
Recently I bought a Ledger Nano S and, not really understanding how or if it would work, I entered the 12 passphrase words. And it worked! There was my Bitcoin in there!
But how does it work? And is there any chance that the Copay team has a copy of these 12 words and could one day raid my Bitcoin? Should I have got the Ledger Nano to generate a new passphrase to be extra secure? Especially as it uses 24 word passphrases. If so how do I move my Bitcoin to be accessed by this new passphrase and not the old one? I also generated empty wallets for Ethereum and Bitcoin Cash. Do these also use the 12 word passphrase I originally entered into the Ledger Nano? If so, how does that work?
Can a Ledger Nano have different passphrases for different wallets held on it? If so, can there be more than one Bitcoin wallet on the same Ledger Nano with different passphrases?
How can I safely get the Bitcoin Cash associated with my Bitcoin transferred over to my wallet?
I am wanting to buy more crypto but want to understand what I am doing before I risk any more money. So any help with this would be greatly appreciated, especially, as you can tell by my questions, I am very much a newbie in this area.
TIA!

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I guess no one has the answers? Or maybe the question is so basic no one can be bothered?
I guess I’ll just have to wing it and hope I don’t lose any crypto.