The Winged Dragon of Ra - Sphere Mode — Ruling

Effetto 0

This card's ATK/DEF is "?". If (original) ATK/DEF are required while it is on the field, its respective values are treated as 0.

Regarding the『Requires 3 Tributes from either side of the field to Normal Summon to that side of the field (cannot be Normal Set), then shift control to this card's owner during the End Phase of the next turn.』text:
This is not treated as an effect. It is the method for Normal Summoning this card.
It is impossible to Normal Set this card (in face-down Defense Position). It is only possible to Normal Summon it (in face-up Attack Position).

About this card's ① st effect:
This effect is a Continuous Effect, which applies in the Monster Zone.
The effect that prevents this card from being targeted for attacks is an effect that affects your opponent's monsters. (Your opponent's monsters that are unaffected by this monster effect can target this card for attacks.)
The effect that prevents this card from being targeted by card effects is an effect that is applied to your opponent. (Even if your opponent's card is unaffected by this monster effect, your opponent still cannot activate its effect by targeting this card.)

About this card's ② nd effect:
This effect is an Ignition Effect, which can be activated in the Monster Zone.
When this effect resolves, Special Summon 1 "The Winged Dragon of Ra" from your hand or Deck, ignoring its Summoning conditions. If the monster is successfully Special Summoned, immediately apply the effect that increases its ATK/DEF to 4000 to it.