Did you upgrade to SNAP v.7.0 , if yes, that’s mean SNSP 7.0 doesn’t support ALOS2, but these are the ALOS, could be imported in SNAP,
Could be done alternately, because the G. phase F. is only for visual enhancement, however step 7. should be done to remove the topo. phase,
Yes, it could be STEP 8. Multilooking then the STEP 9. Unwrapping