A Half Golem is immune to ALL magic except the specified spells so yes, it would be immune to it's own spells except for any spells that are specified.
In a Half Iron Golems case, any fire, electricity or rust effect would still effect it, just like a full Iron Golem.
It wouldn't be up for repair unless it had failed its' save and this became a construct.
And yes, you still get Magic Immunity regardless of whether or not you make your save.
In a Half Iron Golems case, any fire, electricity or rust effect would still effect it, just like a full Iron Golem.
It wouldn't be up for repair unless it had failed its' save and this became a construct.
And yes, you still get Magic Immunity regardless of whether or not you make your save.