Which of the following is the most electropositive element?

The characteristics of elements $X$,$Y$ and $Z$ with atomic numbers,respectively,$33$,$53$ and $83$ are :

Which of the following sequences correctly represents the decreasing acidic nature of oxides?

Given below are two statements:
Statement $I$: The number of pairs among $[Al_2O_3, Cr_2O_3]$,$[Cl_2O_7, Mn_2O_7]$,$[Na_2O, V_2O_3]$ and $[CO, N_2O]$ that contain oxides of same nature (acidic,basic,neutral or amphoteric) is $4$.
Statement $II$: Among $Na_2O, Al_2O_3, CO$ and $Cl_2O_7$,the most basic and acidic oxides are $Na_2O$ and $Cl_2O_7$,respectively.

Arrange the following acids in the decreasing order of their acidic strength: $Cl(OH) \ (I)$,$Br(OH) \ (II)$,$I(OH) \ (III)$.

Which of the following is an amphoteric oxide?