Which pair of elements has the same number of electrons in their valence shell$:-$

Consider the following four elements,which are represented according to the long form of the periodic table. Here $W$,$Y$,and $Z$ are left,up,and right elements with respect to the element $X$,and $X$ belongs to the $16^{th}$ group and $3^{rd}$ period. Then,according to the given information,the incorrect statement regarding the given elements is:

Which of the following is the correct order of increasing density for the given elements?

The increasing order of reactivity among group $1$ elements is $Li < Na < K < Rb < Cs$ whereas that among group $17$ elements is $F > Cl > Br > I$. Explain.

Which of the following sets of elements have the strongest tendency to form anions?

Which of the following pairs has elements containing the same number of electrons in the outermost orbit?