Which property of the alkaline earth metals increases with their atomic number?

Which of the following is least soluble?

$A$ metal $M$ readily forms a water-soluble sulfate $MSO_4$,a water-insoluble hydroxide $M(OH)_2$,and an oxide $MO$ which becomes inert upon heating. The hydroxide is soluble in $NaOH$. What is $M$?

Which of the following alkaline earth metals is the most electropositive?

$A$ metal $M$ readily forms its sulphate $MSO_4$ which is water-soluble. It forms its oxide $MO$ which becomes inert on heating. It forms its insoluble hydroxide $M(OH)_2$ which is soluble in $NaOH$ solution. Then $M$ is

The tendency of forming chloride hydrates of alkaline earth metals is in the order of