The statements regarding Diborane are 
i) Diborane contains 2-centred - 3-electron bonds 
ii) B - H bond is formed by sp³–s overlapping 
iii) It contains two coplanar BH₂ groups 
The correct statements in above are

The terminal B-H bonds are normal 2-centre-2- electron bonds but the two bridge bonds are 3-centre-2-electron bonds. The 3-centre-2-electron bridge bonds are also referred to as banana bonds.

Each B atom undergoes ${\mathrm{sp}}^3$ hybridization and overlaps the s-orbital of H-atom to form B-H bond.

Diborane contains two coplanar BH₂ groups. Diborane has four terminal hydrogen atoms and the two boron atoms lie in one plane. Above and below this plane, there are two bridge hydrogen atoms. The bridge hydrogen atoms are present in a plane perpendicular to rest of the molecule.