Whenever you finish this trance, you can change your season, and you can gain two proficiencies that you don’t have, each one with a weapon or a tool of your choice selected from the Player’s Handbook. You mystically acquire these proficiencies by drawing them from shared elven memory, and you retain them until you finish your next long rest.

-Mordenkainen Presents: Monsters of the Multiverse

I am a little confused by the AND operator here. Which way should this be interpreted?

1. At the end of a long rest the Eladrin can change seasons and CAN gain two proficiencies or keep the ones from before the rest
2. At the end of a long rest the Eladrin can change seasons and MUST gain two new proficiencies other than those from before the rest
3. At the end of a long rest the Eladrin can remain the same season and gain two proficiencies or keep the ones from before the rest. 
4. At the end of a long rest the Eldarin can remain the same season, but then cannot gain new proficiencies.

In other words, is the gaining of new proficiencies contingent on changing seasons or is it separate? Likewise does gaining of a new season require gaining new proficiencies? 

I believe they are two separate interactions, considering Shadar-Kai and Sea Elves both get the prof swapping ability as well. At the end of a long rest an Eladrin may choose to change their season and/or trance proficiencies.

They are both optional, and do not depend on each other.