Hi,
regarding u-turns the road markings are often a good indicator. If there is an restricted area or a solid line u-turns are usually not allowed.

Regarding the roles of two-way route relations like `route=road` or PTv1 bus routes the wiki is correct (https://wiki.openstreetmap.org/wiki/Tag:route%3Dbus#Members). Empty role or "route" for members used in both directions and "forward" or "backward" depending on the way's direction for members only used in one direction. Members should be sorted by connectivity which is always possible for `route=road` relations but not for PTv1.

Anyway, I have updated this part of the road with :lanes tagging and have tried to fix the relations (which were a complete mess) in https://www.openstreetmap.org/changeset/136179636. Hope this helps to better understand the tagging.
Regards,
skyper