A journey is a fixed-length lock: you commit a gecko for a set period, and it earns CRED for every day it is on that journey. Everything on this page is readable without connecting a wallet.
This list is read from the same configuration the staking screen uses, so it cannot drift away from what you are actually offered.
One of your staked geckos is your Captain. All bonus CRED routes through it, it has to be on a journey to hold the role, and you can hand the role to a different gecko whenever you like using the star icon on the staking card.
Yes, with one exception worth knowing before you start. Your Captain cannot be unstaked while your other geckos are still staked - the staking program rejects it outright. A staked position is therefore fully exitable apart from that single gecko: either hand the Captain role to another gecko first, or unstake everything else and take the Captain out last. Nothing is held hostage permanently.
The Immortal journey is the one real exception, and it says so on its own line above.