Does the story of this one happen after A's/Detonation and before Strikers? Or is this like an alternate timeline?
I just skimmed a little on the first chapter and it says Nanoha is 13 years old (dunno why they tried to keep Hayate's age a mistery, since she's supposed to be the same age). It said as well that Reinforce is 4 years old.
Also, Nanoha's friends (Alisa and Suzuka) are registered on the manga's page here on Anilist, so is she still living on Earth during this one?
If I remember correctly, Nanoha was 17 on Strikers, right? If it's on the same timeline, would this be a prequel to Strikers?
On the official Nanoha accounts, it was stated that the events take place after the Detonation.
A small profiles was created for all the main characters. For example, Hayate uses growth magic to conceal her age in order to better communicate with the Bureau's representatives (a 13-year-old girl founding an organization is unthinkable). In fact, they are the same age and are in the same class in middle school.