Does the Magical Star Kanon 100% spinoff fit canonically within the main series? Kanon is featured in a manga and OVA anime spinoff titled Magical Star Kanon 100% in Shogakukan's Weekly Shonen Sunday magazine where she becomes a magical girl.

Is this series considered canon or another continuity (like Neigma?! Neo)? 

If it is canon, where does it fit in the timeline of The World God Only Knows?
It's just a spinoff because Kanon is extremely popular in Japan. You can't call it canon (or should I say, kanon), because it is not based off the material from the manga. However, Wakaki has drawn a few bonus chapters based off Magical Star Kanon, but does not hold the premise for the OVA's story.