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?

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...?