The oxidation number of Mn in the product of alkaline oxidative fusion of MnO$$_2$$ is ___________.

The number of water molecule(s) directly bonded to the centre in CuSO$$_4$$ . 5H$$_2$$O is __________.

The coordination number of Al in the crystalline state of AlCl$$_3$$ is ___________.

The total number of cyclic structural as well as stereoisomers possible for a compound with the molecular formula C$$_5$$H$$_{10}$$ is ____________.