Hi Sathish,
I have tried the mentioned use-case and it's working fine for me (in case of normal Mobile & Tablet mode).
Steps to follow:
- Create a static entity called Month which includes short named month label
- Introduced a Screen aggregate, with source entity as Static Month entity
- Within the screen, define a Dropdown widget, of which the List property is mapped with the point 2 aggregate's output list
- Set the Dropdown widget's Enabled property with a valid conditional statement as shown below
MonthIdentifier = NullIdentifier()

On valid month value selection the defined Enabled condition will yield false value, hence the dropdown widget will set to disabled mode.
See this sample app
Hope this helps you!
Kind regards,
Benjith Sam