Are 3-center-2 electron bonds and and banana bonds same?
The phrase "banana bond" is usually reserved for situations where steric conditions prevent the orbitals of two atoms from aligning properly so that the bond appears "bent" and is weaker than an optimally aligned bond would be.  Cyclopropane is the poster child for such bonds, diborane is not because this description of banana involves only two atomic centers.

It's a different concept from three-center two-electron bonds, where typically the bonds are well aligned but the three atoms bonded together are not always collinear.  This is what diborane does.  The atoms in the diborane bonds are not collinear because we need two such bonds, not because either bond suffers from imperfect overlap.