bleeding and pedal does not go down for the front driver side

Have you tried removing the bleeder screw to verify it is not blocked? Make sure that the ABS unit did not block that port, some vehicles are picky about bleeding and a loss of pressure on one corner from bleeding will trip a valve to prevent fluid loss. If that valve moved it wold block the fluid.

where is this ABS unit?

my dad said that he did not unscrew the bleed screw but the main line because it was too rusted.

This is a picture of the ABS unit. It is mounted forward of the air cleaner box if it has ABS. Some base models did not.
Rusty bleeders are always an issue. If you are not getting fluid I would probably pull the caliper and see if compressing the piston like you were replacing the pads, would push the fluid/air out through the master cylinder.