Dropdown legacy item, need help with it's event system

Hello! I add menu options in dropdown by code, so in editor list of options is empty.
It brings me 3 problems:

  1. Title label is empty from start. Only after I open dropdown and choose something then it fills with the text. It looks like dropdown’s inner event fills this label after it’s completed executing. But it’s empty from the start.
  2. I cannot choose first option (index 0) from the start because it’s already being chosed but default. So “onValueChanged” doesn’t call.
  3. How to set up default dropdown’s option in Start()?

Please help me.