It can only trigger once per turn, but if multiple monsters are summoned simultaneously by one single source controlled by the opponent, all of them will be switched to defence mode.
Ra's attack and defence is equal to the combined attack and defence of the monsters tributed for its summon. You can also tribute other monsters to increase Ra's attack and defence by that monster. When Ra is summoned from the graveyard (monster reborn etc.) it has 0 attack and defence as no monsters were tributed for it
You don't necessarily have to have any monsters in attack position. The monsters you use for the Synchro Summon can be in defence mode, that doesn't matter. What matters is that they are face-up, because you can't use face-down monster for a Synchro Summon.
No, a 'Flip Summon' is a manual change from face-down defence to face-up attack position in one of your main phases. If the monster is flipped from an attack, or by an effect, then this is a Flip, but not a Flip Summon. Therefore regular Flip Effect monsters like Night Assailant will trigger from being attacked, but monsters that require Flip Summoning like Guardian Sphinx will not.
With these monsters I build the Overlay Network I Xyz Summon ...
no. you use ultimate offering to NORMAL SUMMON one extra monster (basically you get to summon to level 4 or lower monsters). To summon the god cards you need to tribute 3 monsters.
he summons a GIANT SPIDER
No, while you control only one monster and your opponent controls 2, they cannot summon anymore monsters. They can still Flip Summon and Tribute Summon (as long as the end results in your opponent having equal monsters as you.)
Cyberdark Dragon cannot be summoned except by Fusion Summon. Cyber Stein does not 'fusion summon' the fusion monsters is summons, it is only a special summon. It therefore cannot summon monsters like Dark Paladin, or Cyberdark Dragon.
Unless they are monsters that are special summon only, level 7+ monsters require 2 tributes.
In Yugioh Forbidden Memories, to summon ritual monsters you need to use the ritual card when you have the three required monsters on the field.
A Synchro Summon is a special summon, so the summoned monster can be in attack or defence mode, just must be face up.
No. Transformation Summon is not an official term so should not be used outside discussion of the Yu-Gi-Oh GX manga. In the manga itself, while the monsters came from the Extra deck, a Transformation Summon was a form of Special Summon only, and not a Fusion Summon. It was never made clear if the Transformation Monsters were Fusion Monsters, or some kind of Effect Monster or a totally new type.