How to remove apps from startup on Android?

Question

Google

Hello.
There is a 4-year-old phone based on Android 4.1.2. On board 1 GB of RAM. If at the beginning of use it flew, now it slows down. This is especially noticeable when loading, which can last up to 2-3 minutes.
Ccleaner for Android showed 7-8 applications in Startup, moreover, those that are rarely used, but are not deleted for the sake of functionality. I suspect they are the reason for the long inclusion.
I would like to hear tips on optimizing the phone:

1. Remove all applications except system ones from Startup.
   
2. Clean the system from real garbage in the form of a ton of extra folders from Applications.
   
3. Adequate task killer.
   

I would like to get the speed of the system similar to what we get when reinstalling the system on Windows or with total optimization, defragmentation and cleaning the registry.
From my experience of solving this problem:
There is no defragmenter for Android due to the use of flash-memory - so, at least they write.
Startup management programs can do their job, but either they start to load the system themselves, being set to autoload, or the next time the phone is turned on / off, all applications load the system again. Boot manager for example.
Extra folders, empty, do not affect the operation of programs in any way, but are restored).
Task killers, killing processes, load the system themselves.
P.S. I have been thinking about resetting the phone to factory settings for a long time, but contacts, applications, etc.
It strains that the extreme Android-Opera hangs when loading, and then it starts, and with other browsers.
Sorry for the multi-bookaf, but while the piece of iron is working, I don’t see the point in changing it.

Answer 1

Startup Manager - Remove all applications except system ones from Startup.

Answer 2

So far, the search for applications has not given anything - everyone does what the taskillers do, but they do not help. But I came across a remark that somewhere in the bowels of the system there is a folder with autorun.