iPhone 4 - Wikipedia
The iPhone 4 received generally positive reception, with critics praising its revamped design and more powerful hardware in comparison to previous models. While it was a market success, with over 600,000 pre-orders within 24 hours, the release of the iPhone 4 was plagued by highly publicized reports that abnormalities in its new antenna design caused the device to lose its cellular signal if held in a certain way.
iOS jailbreaking - Wikipedia
iOS jailbreaking is privilege escalation for the process of removing software restrictions imposed by Apple on iOS and tvOS. It does this by using a series of kernel patches. Jailbreaking permits root access to iOS, allowing the downloading and installation of additional applications, extensions, and themes that are unavailable through the official Apple App Store.