The 12-word seed phrase (which is BIP39) is given to users after their upgrade in 2016.
Wallets created before that upgrade didn't have that kind of recovery phrase. Instead, they had a recovery phrase including 16-17 words that isn't supported by any other wallet.
3) If so, were these 12 words given to you, or did the user have the ability to choose them?
The seed phrase is generated by the wallet.
Super helpful, thank you.