Undersink Plumbing - Question

What is the small tube for ? First time I have seen it.

What is behind the wall?

You were there you tell us. Call out the caulked upside down 1 1/2” tailpiece extension along with the non approved clear tubing.

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a/c condensate drain
to be verified b4 reporting as such
also no clamps for proper securing & tubing prolly not approved material

If that’s what it is where is the air gap?

Thanks !!!
I will definitely follow the Yellow Brick Road

i avoid interpretation & report deficiencies
as depicted in op pix most ahj around here deem the lav drain & vent hole, when present, as adequate air gap…ymmv
this can has been kicked down the road numerous times w/no definitive resolution afaik

I don’t see any vent hole but what I do see it was is called a branch tailpiece. No part of a branch tailpiece should ever be used as a vent in any jurisdiction.

Maybe in some jurisdictions they like to vent before the trap😖