Which of the following molecules contains one pair of non-bonding electrons?

In which of the following molecules/ions are all the bond angles not equal?

The $H-N-H$ angle in ammonia is $107.6^{\circ}$ while the $H-P-H$ angle in phosphine is $93.5^{\circ}.$ Relative to phosphine, the $p$-character of the lone-pair on ammonia is expected to be

Out of $H_2O$ and $H_2S$,which one has a higher bond angle and why?

The correct order of $H-N-H$ bond angles of ammonia,ammonium ion,and amide ion is:

The molecular geometry of $SF_6$ is octahedral. What is the geometry of $SF_4$ (including lone pair$(s)$ of electrons,if any)?