It is not until that.(强调句)中not until算在句首吗,主句倒装吗?

这个不算,Not until eleven o'clock did he come home.他到十一点才回家.Not until last night did I get the news.直到昨晚我才听到这消息.5.Not until his friend offered to help could he do it.他的朋友帮助他,...