1. In case the co-owner of the jointly held flat being your wife disagrees to sell the flat, you won't be able to sell it,
2. In case of divorce and/or while being tn the matrimonial relationship, the flat belongs to both of you and you can decide amongst yourself if any of you want to sell of his/her share to the other co-owner. As per law, both will stand as the joint owner of the flat,
3. As clarified in my earlier post, divorce and joint ownership of flat are not interrelated but separate. You shall have to decide amongst yourself about how both of you shall divide the said jointly owned property or its sale proceeds, if any.