In which of the following is intermolecular $H$-bonding present?

Among $H_2O, H_2S, H_2Se$ and $H_2Te$,the substance with the highest boiling point is,

In which of the following,the compounds are correctly arranged in the decreasing order of boiling points?

The number of hydrogen bonds formed by a water molecule at normal conditions is

Structures of molecules of two compounds are given below:
$(a)$ Which of the two compounds will have intermolecular hydrogen bonding and which compound is expected to show intramolecular hydrogen bonding.
$(b)$ The melting point of a compound depends on,among other things,the extent of hydrogen bonding. On this basis,explain which of the above two compounds will show a higher melting point.
$(c)$ Solubility of compounds in water depends on the power to form hydrogen bonds with water. Which of the above compounds will form hydrogen bonds with water easily and be more soluble in it?

The maximum possible number of hydrogen bonds in which an $H_2O$ molecule can participate is