If there was a plane small enough to fit on a large enough tunnel would it be able to foy, given the different behaviour of the air due to the restricted space? Or a plane just really depends on air inches around it?
Do you mean through a tunnel?
I’m assuming the OP means fly along the length of a long tunnel.
If the tunnel was really, really big, of course. If the tunnel was barely big enough for the plane to fit, in both height and width, maybe (probably?) not. So the question boils down to how large does a tunnel need to be for a plane to be able to fly in it.
There would be aerodynamic differences, just as there are when a plane flies close to the ground (c.f. ground effect). But it could definitely work.
Here’s a runway in North Korea that runs through a mountain. It’s apparently 30 meters wide.
Well if you think about it plane designs are tested in a tunnel, a wind tunnel. The plane is stationary and the air moves around it instead, but it’s essentially the same thing.
but… Is there a treadmill in the tunnel? 
Wouldn’t roof effect cancel ground effect , and therefore its like flying in clear air ?
In wind tunnel testing, the test article is typcally much smaller than the tunnel width, specifically to avoid interactions with the tunnel walls.
Isilder raises an interesting point, but I think he’s got it backwards. The usual ground effect would be present due to the inability of the air to move downward beneath the wings, augumenting the relative pressure increase on the bottom of the wings. However, there would be a complementary “ceiling effect” on the top surface of the wings: the ceiling would prevent air above the wings from moving downward, resulting in a greater-than-normal relative vacuum on the wings’ upper surface. Ceiling effect, like ground effect, would augment lift.
Conventional ground effect is a “negative feedback” situation, i.e. the closer you get to the ground, the more ground effect pushes you away from the ground, so it tends to be stable. “Ceiling” effect when flying in a tunnel would be a “positive feedback” situation: the closer you get to the tunnel ceiling, the more strongly you get pulled toward the tunnel ceiling. This could be potentially unstable; the pilot might need to be very attentive to avoid getting pulled into the ceilling.
One more tunnel effect is an interaction with the lateral walls that would have an effect similar to winglets: the walls would hinder the formation of wingtip vortices, making the wings more efficient at generating lift. This should be a negative feedback situation too: the closer one wingtip gets to its wall, the more lift it generates, causing the plane to roll away from that wall. It might not be stable though if an oscillation develops, with the plane possibly rolling back and forth.
Tunnel size & length do matter.
Planes under bridges, check
Planes through hangers, check
helicopters in & through hangers, check
Ultra light aircraft in enclosed auditoriums, check
Toy sized aircraft everywhere, check
Any sized aircraft down any tube where the walls are within one wing span all around that is over three lengths of the aircraft that did not hit the walls, no so much