Jack believes that they no longer need the conch because they know who to listen to and who to allow to speak. They no longer need to conch to decide that. This shows regression because they learned to effectively choose someone to speak without needing the conch to do it for them.
The suitors believe Odysseus has died and they want to marry his wife. I'm not sure about the second one, sorry.
The quote shows that George is an alcohol an that Lennie who in guessing is his friend is trying to let out for hin