I have 12gb of ram and I've never used all of it, I want to take advantage of the 12gb ram and keep all apps running no matter what unless I manually close the app itself. How do I do this?
What you are trying to accomplish is something better suited with Root where you have Manual control of the threshold of the device. Through processes of Overclocking you would achieve what you are trying to do which, to be honest, I dont really understand unless you are attempting to burn up the phone?? I suppose if I understood the Effect you are wanting, it would make the process of getting you there a little easier
I mean no, I don't want my phone to explode. I just want to keep more apps open than apps closed. The most ram I've ever used was 8gb(I have 12gb ram), and I don't want the other extra 4gb sitting there doing nothing. Is there no other way than rooting my phone?
no. not that I know of. that extra ram is used or is in reserve I should say, so that the phone doesnt start crashing apps. say you had 18 apps open and the limit was 20 (really close) and boom you get a push notification or something large enough to push it over the limit. If the system crashed say your ONE UI or another vital operating feature that most of the overall system is dependent on it could cause your phone to shut down, bootloop, or a number of bad things in between. I'm all about pushing devices to their limits but what you are asking is much like the dreaded "Toomany Windows Open" on a Windows 98 Computer back in the day. Things just dont work right. If you are seriously interested in achieving this though, I recommend heading over to XDA Developers and Rooting (AT YOUR OWN RISK) through Magisk [takes about 5 minutes] then flash in AOSP and grab clockwork mod, make a backup, and start the Overclock process. Proceed with Caution though as you can easily make a pretty Paper Weight out of your device if you do not know what you are doing.