Forum:About Magician's Circle

Hi, I duel a spellcaster deck the other day and a few questions came up with Magician's Circle:

1) When a spellcaster is summoned by Magician's Circle, can it attack immediately? 

2) Also, when Magician's Circle is activated, is it true that both players MUST summon a spellcaster from their deck? or is this optional? 