Can the Dispel Magic spell be Readied to counter an opponent’s spell?

When playing as a spellcaster, is it valid the use of the Ready action to prepare Dispel Magic to counter a spell cast by an opponent? In the same vein, when declaring said action, do I have to specify which spell slot I will use when Readying the Dispel Magic spell? If that is the case, does this tactic nullify an opponent’s spell?

I get the impression that this is basically turning Dispel Magic into a spell with a casting time of "1 reaction". Is my reading of the rules accurate?