You can only activate "Scapegoat" if you have 4 or more vacant Monster Card Zones.
If the effect of "Cyber Jar" is activated during the turn you already activated "Scapegoat" all monsters that could be Special Summoned will be sent to the Graveyard.
If your opponent chains "Magic Jammer" to your "Scapegoat" you may still perform Summons that turn, but if they chain "Imperial Order" you may not perform Summons.
You may offer Sheep Tokens as Tributes for Toon Monsters, since they are Special Summoned and not Tribute Summoned.
If the effect of "Royal Oppression" is chained to your "Scapegoat" your Sheep Tokens will not be Special Summoned and you still cannot perform any Summons that turn.
If you have already Summoned a monster, including a Special Summon caused by the effect of your opponent’s "Cyber Jar" you cannot activate "Scapegoat".
You can Set a monster in the same turn you activate "Scapegoat".
If you control 2 monsters and your opponent activates "Change of Heart" to gain control of one and you later activate "Scapegoat" your monster will be destroyed during the End Phase if all 5 of your Monster Card Zones are still occupied.
If you activate "Monster Reborn" and your opponent chains "Imperial Order" you can chain "Scapegoat" and "Royal Decree" but only "Scapegoat" will resolve since "Scapegoat" will prevent any S
Special Summons, and therefore "Monster Reborn" cannot resolve.