Is there a mobile app or any other way that I can check metro schedules in advance?
There will not be any trains at those hours. The rail hours are:
Monday - Thursday 5 am - 11:30 pm
Friday 5 am - 1 am
Saturday 7 am - 1 am
Sunday 8 am - 11 pm
You can use their Trip Planner to get specific schedule information for a journey, the real-time departure information on the WMATA website (next bus/next train), the live train map, or any number of third-party transit apps for information. The timetables page (switch to the "rail" tab) lists service hours and will tell you the when to catch the first and last trains from any given station ("Station Service Hours"). As WMATA is doing a lot of maintenance and reconstruction, be sure to check the service alerts for changes that may impact your trip.
The trip planner or Google Maps can be used to plan out alternate routes for late-night journeys, but a taxi, Uber, or Lyft may be the best option or only option in many cases.