how many following statements are true?

1) in least squares regression, sum of residuals is always equal zero

2) least squares regression line minimizes sum of squared residuals.

3) residual plot that display random scatter of points is good indication that assumptions in simple linear regression model are valid

4) one assumption in simple linear regression model is that standard deviation of Y is constant for all value of X.

5) one assumption in simple linear regression model is that Y follow normal distribution for all values of X.