Question

Can two OH- group attached from single carbon atom?

Answer 1

yes two OH groups can be attached to a single carbon atom since the valency of carbons is 4.

Answer 2

Yes two -OH can be attached to a single carbon atom, like in carbonic acid (H2CO3) and geminal diols. But they are usually unstable. Geminal diols usually lose a water molecule forming an aldehyde or ketone. And as you know carbonic acid disoociates into CO2 and H2O.