iTunes
Will single song purchasing still exist with out iTunes? Will my previous single songs exist without interruption?
Question marked as
Yes. Also note that Apple is not closing the iTunes Store. They have announced that they will be replacing the iTunes application on the Mac with 3 separate applications with similar functionality this Fall. There has been no announcement, at least so far, that they are replacing the iTunes application on Windows. See the following from https://support.apple.com/en-us/HT210200
The iTunes Store will still be available to buy music on Mac, iOS, PC, and Apple TV.