None of this is true for android. You can and always have been able to sideload whatever apps you want so long as it's compiled to work with your version of android.
Apple has always been the walled garden and they are nowhere near in the same league.
If you want to be taken seriously, don't mention apple and android in the same sentence like this. Apple makes phones, android is an operating system and a Foss one at that. Wording like the above shows a major lack of understanding when it comes to tech.
Do better.