Opera Turbo was always disabled on my phone, never needed it. But I never used GPRS, only EDGE and later.
The iPhone was released June 29, 2007 but announced in January. “On 7 November 2007, Opera Mini 4 was released. According to Johan Schön, technical lead of Opera Mini development, the entire code was rewritten.[28] Opera Mini 4 includes the ability to view web pages similarly to a desktop based browser by introducing Overview and Zoom functions, and a landscape view setting. In Overview mode, the user can scroll a zoomed-out version of certain web pages.[29] Using a built-in pointer, the user can zoom into a portion of the page to provide a clearer view”
Hmm, perhaps I had a beta version of that. I definitely had it before the iPhone came out. Or it might have been a different browser? Not sure.
Opera Mini was well optimized for cellphones of the time and bandwidth limited cellphone plans, but Apple’s deal with AT&T to allow unlimited bandwidth flipped a lot of those design decisions on their head. IMO what really separated the iPhone’s browser was a larger screen + better UI + better rendering + unlimited bandwidth meant it could just be used to casually browse the web.