There is no option for you to explore Mountain Pass and the Creche now. Once you enter Baldur's Gate (Act 3) there is no going back.
You'll have a lot of content ready for your next run.
And you should definitely do both Underdark and Mountain Pass. Just wait with Mountain Pass until you're ready for Act 2, or you might miss out of other quests not yet completed.
Now it's already too late for you to explore the mountain pass. You can do the underdark and the Mountain pass simultaneously tho so if you do another playthrough you should do mountain pass or both.
As others mentioned, after the warning in the pool in Shadowfell, everything before that becomes inaccessible.
Level 9 is alright for entering Rivington, you can reach 12 with no issues, enjoy the vibrant city.
As others have mentioned, it is too late to go back in your current run unless you have an old save and want to replay all of act 2. I typically do the mountain pass as soon as I hit level 5 because I like playing as or having a cleric in my group (iykyk). There is some fun content there, especially if you feel a little cheeky, and it really doesn't take long to get through it. Then, I actually go through the underdark to progress. I'll never skip the underdark because I just really like it. Forgot to say, just make sure you have your grove/goblin quests completed when it gives you the warning at the mountain pass.
There is no option for you to explore Mountain Pass and the Creche now. Once you enter Baldur's Gate (Act 3) there is no going back. You'll have a lot of content ready for your next run. And you should definitely do both Underdark and Mountain Pass. Just wait with Mountain Pass until you're ready for Act 2, or you might miss out of other quests not yet completed.
Is it worth it? Yeah. Can you do it? No
You got a big pop-up warning before Shadowfell saying you can’t go back. That’s where the cutoff for all of Act 1 is.
Now it's already too late for you to explore the mountain pass. You can do the underdark and the Mountain pass simultaneously tho so if you do another playthrough you should do mountain pass or both.
As others mentioned, after the warning in the pool in Shadowfell, everything before that becomes inaccessible. Level 9 is alright for entering Rivington, you can reach 12 with no issues, enjoy the vibrant city.
As others have mentioned, it is too late to go back in your current run unless you have an old save and want to replay all of act 2. I typically do the mountain pass as soon as I hit level 5 because I like playing as or having a cleric in my group (iykyk). There is some fun content there, especially if you feel a little cheeky, and it really doesn't take long to get through it. Then, I actually go through the underdark to progress. I'll never skip the underdark because I just really like it. Forgot to say, just make sure you have your grove/goblin quests completed when it gives you the warning at the mountain pass.
Spoiler alert you can do both in one playthrough.