In the periodic table,with an increase in atomic number,how does the metallic character of an element change?

Which of the following elements is considered as a metalloid?

Which of the following elements is a metalloid?

Statement $I :$ Acid strength increases in the order given as $HF < HCl < HBr < HI$.
Statement $II :$ As the size of the elements $F, Cl, Br, I$ increases down the group,the bond strength of $HF, HCl, HBr$ and $HI$ decreases and so the acid strength increases.
In the light of the above statements,choose the correct answer from the options given below.

$Be$ and $Al$ show similarities in properties due to diagonal relationship except in the property $X$ given below. What is $X$?

In the reaction $2Br^- + X_2 \to Br_2 + 2X^-$,$X_2$ is .......