Can you please elaborate -- if you lose your original Ledger Nano device can you take the private key and input on any device and retrieve your coins?
Afaik, ledger will only generate you seed phrase. You can input the seed phrase on electrum wallet (and many other bip39) wallets to generate your whole wallet with your balance.
Also, the Ledger device gives you a pre-select list of words for the private key.... why is that? Why can't I create my own? Wouldn't that be safer? What if someone hacked in to all the list of private keys from the Ledger company... how is it that the pre-select list of words is really safe if it was loaded don to the device before I purchased it...?
Noncustodial hd wallets will generate you seed phrase for backup which can be used to recover your bitcoin and other funds during wallet damage or lost. HD wallets generate seed phrase which is normal, it is not according ledger company but according to how HD wallet works. You can not create your own seed phrase, wallet automatically generate that for you.
how is it that the pre-select list of words is really safe if it was loaded don to the device before I purchased it...?
The seed phrase is generated after you open the wallet, not loaded to the wallet before you purchase it. You can read wallet part of master bitcoin to understand more about this by clicking the link below. The seed phrase is safe and secure provided if you store it safety and avoid hackers from reaching it.
https://github.com/bitcoinbook/bitcoinbook/blob/develop/ch05.asciidocWhat if someone hacked in to all the list of private keys from the Ledger company
The issue of a wallet to be open source or close source have to be addressed here. Normally seed phrase is safe but vulnerabilities in wallet can make it to still be reached by hackers. That is why open source codes are better than close source because of transparency. But ledger wallet is closed source, you can only trust the company not to have vulnerabilities in the wallet that can reveal your seed phrase but it can actually happen as it is close sources. If vulnerability is in open source, it will be removed because many people are willing to work on it but unlike close source that you do not know the source code, even if vulnerability is in close source, you can not know until your funds are all gone. Although, I am not saying ledger is like that, but letting you knowing how open source codes are better.