Why do elements in the same group have similar physical and chemical properties?

Which of the following substances will liberate bromine when reacted with a solution of potassium bromide?

Beryllium shows diagonal relationship with

Which element has the greatest tendency to lose electrons?

Which of the following electronic configurations represents a coinage metal?

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.