Monotheists, is it plan or prayer?

If there is a plan for each and every person, alive and deceased, it would suggest that there is a grand plan from the beginning of mankind until the end of mankind. Which means, for one to exist every member in his/her pedigree, at least, had to live exactly to their plan. Which leaves absolutely no room for free will - because the slightest of deviations from any one at any point would spoil the grand plan. And if one person's plan could deviate, so could every other's. So regardless of what people believed or knew, they undeniably lived to a singular god's plan. Such is why we are alive today, and such is the case for our grandchildren and so on. For them to exist we had to live exactly how it was planned for us to live. My point isn't necessarily about free will, it's actually to do more with prayer. If every life that has existed and ever will exist has and will live exactly as planned, then why would prayer be necessary or important? Praying for a sign or guidance is redundant, as you are or were automatically living out your plan anyway. Praying for change or good fortune is pure arrogance, because for some reason the one praying thinks, assumes or believes that the god will adjust his mighty scheme to accommodate a single person's request. Just one prayer makes about as little sense as a lot of prayers. If prayers were to be answered then there simply is no plan, and there is only free will. And while we're at it. If one's "plan" was unchangeable and was not made known, then it really isn't a plan at all. We're then living out a scripted existence predetermined and unaltered. Which means we aren't really living, we're just existing, for something else (completely unknown) and it's idea of a material world in a passage of time. Everything everyone has said and done, has already happened, and so the authenticity of each living person is lost. Every achievement, every decision, has already been achieved, and decided for you. All your hard work, and all the credit you could take, has been done for you, and credited to something else. On the flip side, every prayer you make, unintentionally compromises either a living person, or a person yet to be born. So I ask. What is the point in praying to a god that has planned your life out in advance?