We can say:
"Everyone has dreamed of being rich and famous at some time in his life." This means that he dreamed it at some point in time in the past. (emphasis on the action in the past).
"Everyone has dreamed of being rich and famous sometime." This means that he dreamed about being famous at an indefinite time in the future. (emphasis on the future).
"Everyone has dreamed of being rich and famous some day." This is equivalent to using sometime above, (emphasis on the future). It is the more common way of expressing it in my opinion.
"Everyone has. at some time, dreamed of being rich and famous some day." This expresses both emphases, past and future.
"Everyone has. at some point, dreamed of being rich and famous some day." This is what I would probably say, I think.