Both Assertion and Reason are true but Reason is not correct explanation of Assertion. Alcohol forms hydrogen bonding and it also has a covalent character, so it is a polar solvent. So, due to polar nature lithium chloride and magnesium chloride are soluble in polar solvent alcohol. Due to diagonal relationship, Li and Mg show many similarity in properties like electronegativities, harder weak bases etc. But this is not a correct explanation of their solubility in alcohol.