I've never seen popcorn on a wall. It isn't sturdy at all even painted. You would walk by it and brush it right off. I think you are seeing heavy texturing. Orange peel or heavier. Probably poorly done. This is acutally like drywall compound, sprayed on and troweled off to get different types of texture. It's very common where I live. It means the drywallers do not have to be skilled at taping and sanding. This doesn't come off like the popcorn. If it's really bumpy you can sand it down and retexture. You can also float new mud out to get a level surface. But now you need the same skill as a good drywaller. If it is just one hallway and not the entire upstairs, I would just take my time and sand down as much as I could. Or have a drywaller come in and take a look at it. They will probably be able to do a much better job. Just ask them how they usually finish walls. You don't want someone who only textures. Gloria

That's going to look so pretty! I would paint the pass-through the same tan as the kitchen wall...and when you say "walk-through," do you mean the untrimmed doorway? If so, I would also use the tan. It will probably read a half-shade darker than the kitchen wall does, because of the shadow, and I think that will mark the transition really nicely, and set the new blue room off as a separate space more clearly.

I like the abrasive blasting idea. I'd waterproof it and install tile. Or better yet, wire brush it and install solid surface.

I am seeing a sea glass green/gray on my monitor..Yes? Wondering how you will recline with the sofa against the wall.