[Xposed Framework Modules] doublehp:
You can not. Pin codes have variable size; most often 4c, but can be more.

Some very specific apps could do what you want, when they handle the code inside their own conf; they can't do it when password to match is on external ressource (or via a system lib).

Plenty of apps on Play can do it. I have no particular name to give you, did not install any, but, saw many. Search things like

- silent down

- flip silent

- move actions

- flipover

- face down actions

- Tasker

It could be possible; but very unlikely any one will take time to do. I understand why you want that; honestly I do: you want to cycle your batt, and this is very good idea. I know how to read charger caps in /sys, but never found how to control it. It heavily depends on kernel, but there is a software part in /system; so, by playing with the apropriate lib, or app, it could be possible to do so.

NO NO NO.

DON'T DO THAT , NEVER.

1: when cam is hot, it's unreliable; thermal noise will kill picture quality.

2: is cam gets REALLY hot, from around 90°C, it could burn, produce shortcircuit, and then ... shortcircuit your battery, and make the phone start fire, or explode.

I AM NOT JOKING, I AM PERFECTLY SERIOUS.

And 90° on CCD is perfectly possible to reach. If you leave in a hot country, the env temp could be 50 or even 55°C. Then, add the energy brought by sun light ... it can easily add the 40° to kill your CCD.

Any way, reason 1 is already a suffisant reason.

Not possible.

Apps are ... managed by "Android", and, for most of us ... Dalvik.

Xposed modules usually alter system files, and conf files; so, most of the modules are not even "running". They just alter /system. In some rare case, they have a running process, which is usually run like a classic Linux process.

You can not convert an APK app into a classic Linux process. They are hugely different by design. Apps are designed (not by people who dev apps, but by people who conceived Android) to be stopped at some time, for various reasons (since Android 2; Android 1 allowed you to have unkillable apps; now, since andro 2, all apps can be killed).

Apps that are unkillable are not really apps. The app is a fronthead that will ask root shell, and then, start a Linux process. Permanent apps need root, and are designed to be permanent (ans still, sometimes they fail, and stop).

Some "call blocker" apps can also block messages; you want to block from "unknown numbers" and "numbers not in contact list". You find that in Play.

Also, my phone service provider ... has an anti-spam app. When one user get's a spam, it declares the message as such via the app (process is ... not trivial; gotta launch the app manually), then, sms is uploaded to some national service, and the, number added to blacklist; then, other users can download the blacklist. This process involves two companies. Those companies are national; so, quoting the app name would be useless for you. But, yes, it can be done.

Very interesting; if you find it, please tell me.

In short, you want to alter the default icon for people not in your contact list, and ... then, set again a different icon for unknown number. I like your idea.

Maybe ... you should directly contact dev of 3rd part apps for phone. I will submit your idea to the one I use: exDialer.

See above.