TabBarController | TabBarController acts like a UITabBarController | iOS library

I'm a little stuck with this one,

I have a logout button on my app and when I tap it I want to change the selected tab of my tab bar controller to the tab that's selected when the app loads up (index 0) (this should trigger the "sign in to continue" view)

A little more context

My app's root view is a TabBarController and each tab is declared like this:

I am an iOS developer, So I have idea how TabBarController works in iOS. Now I am working on Flutter (First APP).

I have an App which uses CupertinoApp-CupertinoTabScaffold-CupertinoTabBar to persist BottomNavigationBar in every nested screens.

My App's hierarchy

I have some weird problem with tableView.keyboardDismissMode = .onDrag. I lift up my view when textField tapped it's ok. Then I want to dismiss my keyboard exactly like in iMessage, but in my case when keyboardWillHide notification called view.frame.origin.y not equals 0. It's equals 12. Fun fact my code works pretty cool in simulator but this bug only on real iPhone 11. Any ideas what the hell is it?

My code with keyboard notifications

Currently I have a TabBarController with some tabs in it. However if I try to open another TabBarController with tabs as a popup (code below), the tabbars just stack. I have tried using TabBarcontroller?.tabbar.ishidden = false. But it just hides the previous tabbar, without removing the spacing. Like the new tabbar is above the hidden space (constraints still there). I just want it to popup overtop of the previous controller. Also in case you are wondering, I am opening the VC from one of the First Tabbar controllers. FYI, the tabbar backgrounds are clear so thats why they look like that.

I am having trouble with 'MyTabBarController' being pushed too far off the screen. I have a normal View Controller, with a button that opens 'MyTabBarController', as essentially a popup over the screen. I have no problem with this code for a normal ViewController, but with a TabBarController + Embedded Nav Bar its causing some issues. The tabbar is also pushed off the bottom of the screen. Im sure it has something to do with the frame constraints, but not sure how because I have tried different tactics. The frame of the popup is equal to the frame of the previous view so I am a bit lost on what to do. If you need additional information let me know.

I have an arrangement of views in my interface builder (image).

Red: My root TabBarController that segues to...
Yellow: My UINavControllers that have embedded...
Green: View Controllers

I was trying to add code to TabBarController.swift to change how my ViewControllers.swift are presented (modal presentation code).

In TabBarController.swift

The app keeps crashing whenever I tap the push notification when the app is closed. If it's in the background or open when I tap the push notification then it loads just fine.

I've tried the suggestions over here: Swift - How to open specific view controller when push notification received?

Below are the relevant functions in the app delegate. Any print functions to determine where exactly the crash is caused is not being registered so I cannot debug properly. The only message I see is:

Message from debugger: Terminated due to signal 9

Been scratching my head for a day trying to get this to work. I was receiving the notification but never navigated to the specific tab when clicked.

I have several views. Here's what it looks like: First view is StartViewController (arrow), which opens TabBarController which is owner of two other views - FavoriteViewController and MapViewController. How to close all of them and go back to the StartViewController? This should work like starting the app from first view. I found similar question, but unfortunately it doesn't work. How to go back to the initial ViewController the right way?