Manual Camera App for Android KitKat 4.4.4?

I decided to get into smartphone photography with my Android phone and there are some pretty good camera apps that help take good quality photos, but the apps lack quality features such as, shutter speed, aperture, focal length, and other essential manual features. I did do some research on manual camera apps and I did find apps that offer manual camera controls, but they were for Android 5.0+ and rooted devices. I do not own a device with Android lollipop nor have a rooted phone and/or plan on rooting it due to the difficulties of rooting my device. So, I wanted to know if there is a manual camera app like Manual Camera, but for Android 4.4.4. I already tried Camera FV-5 and that did not offer shutter speed and aperture controls. Btw if such a Play Store app does not exist is there at least like a link to an app or private app? (Idk what apps that are not on the Play Store are called)

Device Specs: ZTE Zmax Android 4.4.4 Not rooted

Camera Focus not working (Manual & Auto)

So since I updated to OxygenOS 2.1 my camera focus has stopped working, I've tried the stock camera app, Open Camera and Camera360, none of them can use the focus, neither manual focus or auto focus.

I've tried both wiping the cache and a factory reset, neither of which worked. So what do I do now? Is it possible to roll back the OS to 2.0.2 or 2.0.1? Should I install(reinstall?) 2.1 again? I'm very noob when it comes to tinkering with my phones OS in this kind of way. I really do need to get this sorted, so if you tell me what I need to do either give me a noob-friendly description of how to do it or link me to a noob-friendly guide for this stuff. Really out of my comfort zone here, so afraid of bricking my phone(first nice phone I've let myself buy in years).

Phone is not rooted.

Full manual controls on HTC One M7

Is there any way to get full manual controls on One M7.