How many numbers of following statements are correct? 
i) When pure $\alpha -D-$ glucopyranose is dissolved in water, its optical rotation slowly changes.
ii)  $\alpha -D-$ glucopyranose and  $\beta -D-$ glucopyranose are anomers
iii) Methyl glucosides do not react with Fehling's or Tollen’s reagent
iv) $\alpha -D-$ glucopyranose react with $NaHS{O}_3$ to form white precipitate
v) $\alpha -D-$ methyl glucoside and $\beta -D-$ methyl glucosides are anomers
vi) Reduction of Fructose with $Na-Hg /H_{2}O$ gives both sorbitol and mannitol