Without the app store ? Is that even possible?
yes - totally possible - it’s how proprietary apps for employee use in large companies are distributed.
Yes, but the iPhone has to have the Enterprise system turned on, and set-up to accept the pushed enterprise Apps. Chinese third-party app stores were using this approach by using enterprise certificate to sell unauthorized apps. The user has to download the enterprise certificate then accept the apps.
This is a non-story. The exploit requires social engineering iPhone users into installing an app outside of the Apple App Store.