Has there ever been a time? Yes, when God said "now I know" that says before "now" God did not know.
Are you than going to say when God asked for where Adam was in the garden, He literally needed directions to him?
Yes, God can learn. If He has chosen not to know something beforehand, then He can say when Abraham sets his mind on killing his son Isaac, now I know.
What would He had done if Abraham decided to go ahead and kill of his son?
Third question, broken up into parts:
a) Did God cause all things? Yes, directly or indirectly. He created man with the ability to make autonomous choices, so when we make autonomous choices, He is the indirect cause. But because they are autonomous, He is not the author of sin.
b) Does God have perfect foreknowledge. Here we must define what you meant by "foreknowledge." Foreknowledge in the modern dictionary sense means knowledge of the future. If this was your meaning, God knows the future exhaustively, then no God does not have perfect foreknowledge because He has chosen not to know some future things, such as Jesus not knowing the time of His return.
while on the earth, Jesus chose to "limit" Himself, part of Him "emptying" Himself..
Thus , while on earth, was operating fully as a man, not dependant on his God nature, so he would Not know the date, as was not imortant to doing His work on earth...
Trust me, Once back to Heaven, at Fathers right hand, now know everything once again!
But if by "foreknowledge" you were referring to the biblical usage, of knowing things declared or predestined in the past, and these things predestined have not yet occurred, then His knowledge of those future things is indeed perfect, He will bring about whatever He has purposed for no plan of God can be thwarted.
c) Does God exercise direct control of some things? Yes. He intervenes and brings about His purpose and plan. Has God chosen to directly control all things? No, because His purpose requires that we make autonomous choices, so He does not directly control our autonomous choices, such as to repent. Thus when we repent, we bring glory to God, fulfilling the purpose of creation.
d) Yes, God is free to do as He pleases, and He has chosen to directly control some things, and to allow other things to occur even when they are inconsistent with His desire. Rather than cause all men to be saved using irresistible grace, God allows men to believe or not believe in Christ autonomously, and then He chooses to save those whose faith He credits as righteousness, because that is according to His purpose and plan.