These instructions are only applicable to some Samsung Android devices, not other Android devices, not iOS devices.
For other Androids, you've gotta root.
It explicitly voids your OEM warranty (which matters if/when you want to return, repair, or resell the device through the OEM).
It implicitly voids your Carrier warranty (they don't like it but they also don't care, they can't detect it if you're savvy, and they can't/won't do anything about it anyways).
On many (not old) devices it also invalidates Google's Trusted Root Certificate Storage. In theory this means your device security is fundamentally compromised at the top hardware/firmware privilege level. In practice it means Google Play Store and Google Services (and any software which relies on them) will nag you at every opportunity (because you mistrust Google, you paranoid villain!) - unless you just download/sideload/crossload the app APKs directly through an SD card or USB/sync connection. But do yourself a favour and run everything through antivirus/malware scan before running or installing it - the risk is very low (with clean APKs from legit sites) but the consequences can be catastrophic (password theft/keylogging, ransomware lockout on your data, "permanently" brick your device, even infect/infest other trusted devices) once something bad sneaks through the door.
And with ultimate power comes ultimate oops. The user has full access to everything - including system files which are normally hidden or protected for good reason - and can easily muck around or break stuff. Hard-reset back to factory default can (almost) always save the day, but it can also be a pain.
OneClickRoot (baseon the venerable su-exploit) is, I think, the best option. It basically asserts itself as the highest-tier app (just below the OS level), loads itself before anything else, and allows/denies/controls other app execution or permissions as the user specifies. Stable, lightweight, simple, free. It's also functionally similar to a task-killer because it simply prevents garbage you don't want to run from ever running.
For iPhones, you've gotta jailbreak.
I think this is basically just the iOS counterpart of rooting. I know it usually gets Apple to blacklist your device but I otherwise don't know anything about it.
Most people buy iPhone because it "just works" the way Apple wants, without any preinstalled non-Apple junkware, so apparently not much motivation for jailbreaking.
Don't forget that all the built-in apps are just apps. Stuff like Dialer, Messaging, Contacts, Browser, Clock, Calendar, etc. Even media files (wallpapers, ringtones, notifications, alarms, system sounds), startup and shutdown animations, etc. All of these things can be replaced by apps or files of your own choosing - all the ones you dislike or won't ever use can be removed to free up space.
