The independence of the residuals can be checked by analyzing certain charts or by using the Durbin-Watson test (under Time Series menu). For this, you need to activate the respective test in the Test assumptions sub-tab. The normality of the residuals can be checked by analyzing certain charts or by running a Shapiro- Wilk test on the residuals.
Use the various tests proposed in the results of linear regression to check retrospectively that the underlying hypotheses have been correctly verified. Validation of the hypothesis of linear regression
The variables are then removed from the model following the procedure used for stepwise selection.