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?
Yes. But you're supposed to use the mnemoric seeds to restore your private keys.
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...?
No. The mnemoric seeds are generated by the device's with randomness, they're never preloaded or generated by Ledger and Ledger should never know or have access to your keys. Ledger uses their secure element as a source of randomness.
Humans tends to be very bad at selecting words from the text. The biasness present in every selection, no matter how random you think it is will always result in your security being compromised. It is much safer for the device to generate the seed for you.