Disbelief Action

[madhopper50]

Need some help in clarifying the disbelief action.  "A character disbelieves an image or illusion by winning IQ against the caster".  Defender: "A defender can react to ONE attacker but loses his next turn".  Does a player lose his next turn if he tries to disbelieve immediately after the Mage casts the spell or does he wait until his next turn to try to disbelieve?

[madhopper50]

"Summoning calls a being from a different plane. The being appears within two spaces of the caster and does nothing on the turn it appears". Does an Illusion attack on turn it's created or the next?  Also, can the character move prior to disbelieving?  Or is disbelieving his only action?