Backstack like instagram with viewpager and BottomNavigationBar

Question

I have created an android app (Sample APK & Github Repo) where I implement a BottomNavigationBar with ViewPager. Navigation is ok but I don't know how to handle the back stack in a viewpager like Instagram.

I tried the below code but this way I have to create an unnecessary fragment where I never navigate.

 view_pager_main_activity?.currentItem = view_pager_main_activity.currentItem - 1

suppose I just launch the app to the 1st page and then navigate to the 3rd page by BottomNavBar but now if I click the back button, I go back to the 1st page through the 2nd page. So this way I create the unwanted 2nd page.

Here is the whole back stack process onBackPressed()

override fun onBackPressed() {

       if (view_pager_main_activity?.currentItem == 0) {
            if (view_pager_main_fragment?.currentItem == 0) {
                val recyclerView = findViewById<RecyclerView>(R.id.listRecyclerView)
                val appbarHome = findViewById<AppBarLayout>(R.id.appbar_home)
                val layoutManager = recyclerView?.layoutManager as LinearLayoutManager
                when {
                    layoutManager.findFirstCompletelyVisibleItemPosition() == 0 -> {
                        super.onBackPressed()
                    }
                    supportFragmentManager.backStackEntryCount != 0 -> {
                        supportFragmentManager.popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE)
                    }
                    else -> {
                        layoutManager.scrollToPositionWithOffset(0, 0)
                        appbarHome.setExpanded(true)
                    }
                }
            } else if (supportFragmentManager.backStackEntryCount != 0) {
                super.onBackPressed()
            } else {
                view_pager_main_fragment?.setCurrentItem(
                        view_pager_main_fragment.currentItem - 1,
                        false
                )
            }
        } else if (supportFragmentManager.backStackEntryCount != 0) {
            super.onBackPressed()
        } else {
            view_pager_main_activity?.currentItem = view_pager_main_activity.currentItem - 1
        }
    }

I want back stack navigation as same as Instagram so I tried this way but has deprecated. I don't know how can I achieve that.