Hi Moiz,
Yes, glycogen is a polymer of glucose. No, during glycogen breakdown, water is not used to break apart glycogen. Instead, an inorganic phosphate is used to perform phosphorolysis via a enzyme called glycogen phosphorylase. We then get glucose-1-phosphate subunits after phosphorolysis (not glucose). These subunits are then converted back to glucose-6-phosphate then glucose.
Hope these help!