Which of the following statements are correct concerning the CAPM regression?

$1.$If beta equals $1,$ the security is risk$-$free.

$2.$ R$-$squared is the proportion of market$-$wide risk in the security$$s total risk.

$3.$If alpha is positive, the stock has performed better than predicted by the CAPM.

$4.$If beta is smaller than $1,$ the security is less sensitive to systematic risk than the market average.