Which metal does not react with oxygen even at high temperatures?

During the reaction of some metals with dilute hydrochloric acid,following observations were made.
$(a)$ Silver metal does not show any change.
$(b)$ The temperature of the reaction mixture rises when aluminium $(Al)$ is added.
$(c)$ The reaction of sodium metal is found to be highly explosive.
$(d)$ Some bubbles of a gas are seen when lead $(Pb)$ is reacted with the acid.
Explain these observations giving suitable reasons.

Which of the following is $NOT$ the correct order of reactivity of metals?

Which gas is produced when a base reacts with a metal?

$A$ metal $M$ forms an oxide with the formula $M_{2}O_{3}$. It dissolves in both dilute sulphuric acid and dilute sodium hydroxide solution. Identify the metal and write the chemical equations for the reactions involved.

Which metal is more reactive than magnesium $(Mg)$?