question : SaaS style URLs , HMVC , Dev Footer

Hi All,

I am starting out in CI4 and have 3 questions :

1.
My project is a SaaS type project and currently in CI3, I use this:

    //if(isset($_SERVER['HTTPS']) && $_SERVER['HTTPS'] == "on"){$ssl_set = "s";} else{$ssl_set = "";}
    //public $baseURL = 'http'.$ssl_set.'://'.$_SERVER['HTTP_HOST'];

but in App.php in CI4, it only  excepts a function or a constant -- so how do I set this up  so that I can use multiple URLs ?

2. 
I currently use the HMVC plugin, so each module currently has its own controllers/models/views
How do I achieve like this in CI4 ? -- a small example if possible ..


3.
How do I get to show that development footer :