1 - is It possible with Network extension Framework to connect a unknown Wifi without user interaction?.
Yes.
2 - The background process NEHotspotHelper is It called only when the user enter to Wifi settings? Or is It called when the iOS searches for networks too?
Yes. Your hotspot helper is called by the OS at various times so that the OS can determine which hotspot helpers can deal with which networks.
IMPORTANT NEHotspotHelper was designed to enable apps that help the user navigate a hotspot (that is, a network where access to the wider Internet is gated by some authentication process). You should only continue to pursue this path if that accurately describes your intended use case.
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