I'm not sure what you mean by God's "Master Plan" but there are occasions when some prayed in the Old Testament, that God changed His mind.
Yes, of course God knows our thoughts. God knows everything. Though God knows everything, He still desires our fellowship and this is what prayer is. What if the person you loved never once spoke to you or asked you a question just because you already knew what she was going to say? Likewise, why would anyone who truly loves God expect Him to cater to our whims? God is not a genie in a bottle. He is a Person with feelings just like He created us with. And, this God whom you do not know or doubt, has revealed Himself in His written word, the Bible. Also, by sending His Son, Jesus Christ on a mission that you will understand if you open up the first page of Genesis to find out how mankind got into the mess we've been in since creation. Yet, it did not take God by surprise, and already put a plan in affect long before you and I came into existence.
When I talk to God, I have understanding what a joy and priviledge it is that God wants to hear from me! Because, He loves me...and He loves you. As far as expecting God to cater to my whims, is not what being a Child of God is about. It's about "relationship" and a healthy relationship made possible only because of what Jesus did for us on that cross. I encourage you to get a Bible, read it thoughtfully and ask God to reveal the truth to you about who He is, who you are, why He made you, how this world has gotten so bad, and what He did to rescue those of us who will just simply believe Him! You see,. unbelief has always been the wall between God and man. The Bible tells us that whoever will know God, must believe that He exists and that He is a rewarder of those who diligently seek Him. You can do this by consistently reading the Bible, starting in the middle....the New Testament and find out who Jesus Christ is and what He accomplished for us. You can ask God yourself, with humility, no claiming to have all the answers, but that if He exists, He will help you realize that He is real....the God who is bigger than our finite minds, who is eternal - always existed - which is mind boggling - and is really not that hard to find or know....afterall, He paid a high price so that you could know Him yourself on an intimate level.
There are many religions and philosophies in this world since the beginning of the world......but God is not a religion. This is man's idea. I have studied most of them, and I can assure you by my own testimony that Jesus Christ is who He said He was....and the Bible can be trusted as God's Word regardless of the naysayers and skeptics, because God has changed my life drastically over the past few years. He healed my inner wounds, provided for me financially when I could not work in miraculous ways! He has done more than I could even ask for....and those were not whims!