Hi, I have a mountain home built in the 60's. I recently decided that I want to update my flooring with a wood floor. After lifting up my carpet I found a layer of linoleum meant to look like little pebbles. It gave me quite a laugh.

Anyway, under that is a tongue and groove wood floor. I live in a tri level house and it is meant to look somewhat like a cabin. What I mean is I have wood paneling (that I have painted cream) and this "bottom" wood floor is the ceiling for the rooms down stairs. All of the ceilings in my house are composed of wood.
My question is can I use this bottom layer of wood flooring as just what it is, wood floor? Or is it really just a sub floor that someone made to look nice from below. How can I tell if it is ok to use as my main flooring. I hope this makes sense! I will attach a few pictures of the wood floor from looking up at my downstairs ceiling.
Pictures 1 and 2 are looking up at the wood floor from my lower level rooms.
Picture 3 is looking up the stairwell. It shows both the wood floor on the bottom level as well as a glimpse at the wood ceiling in the upper level.
Picture 4 is looking at the ceilings of my top level rooms.
I am hoping I can use this flooring. That way I save the expense of putting in a new floor.
Thank you in advance for all your help.