For those that embrace a monotheistic world wherein ONE Designer has laid out a plan in advance (can you say predestination?) for all of creation, there's several words that simply have no place with an OMNIPOTENT Designer. That Being is neither LIMITED, able to FAIL, nor one who could be viewed as a RISK TAKER! But, I beg to differ with that ancient Augustinian paradigm.
Because the classical position by the church as been one of embracing POWER and CONTROL, we somehow have projected that upon this monotheistic God. God's a control freak, but, because he's God, it's somehow okay. In the same breath, we say that Jesus is the EXPRESS IMAGE of God. Jesus himself said that when we see him, we're seeing God, the Father.
So, let me ask you a question then.
Was Jesus a control freak? Did Jesus exercise POWER or did he exemplify LOVE? You know the answer! But our EGO wants to embrace and use the POWER!
There's a big difference in HAVING power and EXERCISING power. Once again, look at Jesus. He said that he could call upon a dozen legions to demonstrate his power; however, he chose to exercise his love and show us what unconditional love can do- CHANGE THE FRICKIN WORLD BABY! 
Thus, let me answer the questions posed in the title. Is God limited? You bet your booty! But, He chose to limit himself and thus in a sense he's limited only by his choice to be limited. Can God fail? Duh! Look at the world around us. is this what God would want? When God chose to give us FREE WILL he was not only taking a RISK (love has choices or it's not love), but he was risking failure.
The GOOD NEWS is that the FAILURES are only temporal.
In the end God wins! We win- we ALL win! God takes that which was meant for evil and makes it damn good! We're not diminishing God in any form of fashion by saying that God is limited because it's his own will that's doing the limiting. God's omniscience knew the risks, saw the failures, but ultimately because God is LOVE, he had to hold back his POWER (omnipotence) until the two minute drill.
Hail Mary!