Here are all the commands you need for the first assignment.
GRAPH
/SCATTERPLOT=X WITH Y.
REGRESSION
/DEPENDENT Y
/METHOD=ENTER X .
GRAPH
/SCATTERPLOT (XYZ)=X WITH Y WITH Z.
REGRESSION
/DEPENDENT Y
/METHOD=ENTER X Z
/SAVE PRED RESID .
CORRELATIONS
/VARIABLES=Y X Z pre_1 res_1.