1. For that, please start by working and uploading them separately. 
2. `source=` is not forbidden to be funny. Eg `source=brain`. 
3. For information, I'm undecided on adding `motor_vehicle:backward=no` to contra-flow bus lanes due to historic reasons, overlapping meaning, and uncertain compatibility with `oneway=yes`. JOSM gives a warning to this, which I'm still willing to ignore. 
4. `placement=transition` is only used on sections where the alignment doesn't fit. So not the entire road section. I use it at merge and diverges. 