Looks like your “no” is really a “yes”. Why deny it? My Mormon friends readily admit it when I’ve asked.
You asked a doctrinal questions and Got a doctrinal answer, you did not ask what I believe, I believe he was, but that is something that is not "Doctrine" of the church because the prophet and General authorities of the the church have not come out and said it was "Doctrine" we do have a strict rules about how something becomes doctrine.
IF you would like to talk about my personal beliefs, then i would be happy to oblige as long as you admit that I am the ultimate arbiter of what I believe. There are far to many on this forum who would tell you what I belive for me when in reality they cannot know.
These confessors of another's beliefs also commonly will then argue with me about what I believe, and or try to seer the conversation to their pet stumbling block, so if you want to go there, be prepared for lots of interference from third parties who do not want you to know what I believe for fear you will pray about it and receive a revelation that it is true. it is much safer for them to stick with Mormonism can be true because of X when they do that they are safe, no need to change, for many believe that God authorizes sin by requiring only faith not obedience to his commands.
Anyway, yes, I personally believe that at some point in the eternities God was once a Man living on a world similar to ours.
BTW how much do you know about temporal mechanics for we will undoubtable get there. Let me give you an "Exercise" to think about...
IF something is not bound by time and at some point it comes into existence, is there ever a point in time at which it cannot be said to exist? (The correct answer is no.)
Even if God "Became God" some when, as soon as he exists outside of time, he has always been God.
There will undoubtably be many who will call me all sorts of things for this example, but it is an accurate exercise in temporal reasoning which is why God would explain things to the simple minded peasants as I am from Everlasting unto Everlasting, From all eternity to all eternity and so forth.