Detail Task View
When you tap a task, you'll go into detail task view. On top, you'll see title of your task. You can tap there and edit if you want to. Also you can tap the circle to check/uncheck. Below the title, you'll see due date, icons and list name. You can swipe to see 'Quick Actions' on left and 'Subtasks' on right. You can tap arrow on bottom right to move between tasks on the list.
You can swipe left/right to go into certain views directly from the list. By tapping icons on top will let you move around views easily. Swiping inside task view will let you move between views too.
Start dates, Due dates and Duration
Start Dates can be turned on inside 'Settings > Preferences'. If you have a due date, you also have start date and duration. Normally it's setup to be same. If you change your start date, duration will be shown accordingly. Tasks that aren't due yet but if start date has past, it'll be shown on the date list.
Quick Actions include quickly editing due dates, changing lists, priorities, adding/removing/switching tags, duplicates and etc. Quick Actions can also be used on 'Bulk Actions'.
Check Subtasks document for more details.
On macOS version, you can select from 2 different types. If you check ' > View > Integrate Panels', you can have Quick Actions and Subtasks at the bottom of right pane. If you uncheck it, you can have Quick Actions Panel and Subtasks Panel separate from main window and arrange it as you like.
While using it integrated, you can adjust height by dragging line above the icons. Also you can use keyboard shortcuts (CMD-/ for subtasks and CMD-K for quick actions) to move between views.