This is incorrect. There are spells in the game that are considered universal spells that affect spell-immune units (hence the term "universal"). Universal spells include ultimates and healing spells.WC cannot make a difference between ultimates and non-ultis. And spell immunes are immune to ALL spells...
This is 200% impossible.
That's because he has Resistant Skin.Well I think spellimmunity only blocks some abilites for example YOU CAN NOT DOOM a spell immune creature since otherwise you could doom infernals.
Your settings must be off. In the case of FoD, you can target a spell immune unit and it will fire, but it will deal 0 damage.You can FOD (finger of death (Acrhimonde)) spell immunes some times but that depends on its settings.
Death and decays seems not to affect spell immunes to.