[Rutherford]

The disputing compound is attached. I know that it is unstable because the bonds between 2 sp2 hybridized atoms and 2 other C atoms are 90°, but I need to know how much unstable it is. Very unstable, or not? Can it be isolated at standard conditions?

[Arkcon]

Given that it is purchasable, then it is likely reasonably stable.  Depends on real-world definitions of stable.

http://lmgtfy.com/?q=Bicyclo%5B4.2.0%5Docta-1(6)%2C2%2C4-triene

[Rutherford]

Ok. How stable is this compound:

[Schrödinger]

2 benzyne systems have been known to combine with each other via a [2+2] cycloaddition, to give a system similar to this, except that you have another benzene on the other side of the cyclobutane as well. So this one I feel, would be a bit more stable than that.

And the 2nd compound you've posted now, I guess it is on the same lines as the 2-benzene system, since both the Carbons on the right are sp2 hybridized

[Rutherford]

Thanks for explaining this.