The Azure Span Tour

When you accept the quest for the dragon racing "tours" you will get credit towards all steps you already completed (for example when you did previous racing worldquests in this zone). This will however not happen if you are in a raid group during the time you accept the quest and leaving group will not grant credit retroactively. So make sure you aren't in a raid group when you accept the racing tour quests and if you were, abandon the quest and pick it up again to be granted credit for already completed steps of the quest.

I'm not sure but it seems like you have to try out the race for the Vakthros Ascent...doesn't appear to be a practice course.

Just a small tidbid in case anybody is confused on how you actually unlock the race / advanced races for a specific zone

To unlock the advanced races, you need to do all the standard "tour" quests in sequential order:
The Waking Shores Tour,The Ohn'ahran Plains Tour,The Azure Span Tour,The Thaldraszus Tour
Once you do that, you have to do all the advanced tours in sequenctial order:
The Waking Shores Advanced Tour,The Ohn'ahran Plains Advanced Tour,The Azure Span Advanced Tour,The Thaldraszus Advanced Tour

However, as long as you are not in a raid grouop when you pick up the quest, you will automatically earn completion for races you have already completed. So if you've been keeping up with world quest races, you've probably already completed most of the standard races.