Where in the Bible does Jesus ascend to God as a child?
Oh, wait, you mean this is prophecy and things like temporal sequences aren't always to be taken hyper-literally?
The Greek word used in Rev. 12, teknon, is translated "child" not "infant". There is no connotation of age in that Greek word. It's a generational word. We are called "children of God" regardless of our age. See Act 13:33, "Thou art My Son (teknon); today I have begotten Thee."
There are other Greek words, nepios and paidion, used to convey the age of the child cf. Matt. 2:8; Luke 10:21; 1 Cor. 13:11, Heb. 5:13. These Greek words are not used in Rev. 12.