Hi Muhstasim Haque Shadab,
1. The value of zero may cause errors in some calculations, so a better approach might be to use weather data from a different file for the time stamps you are not using.
2. This depends on what performance model you are using. Please see the "Weather Data Elements" topic of help for a table of weather data required by the different performance models:
samrepo.nrelcloud.org/help/weather_data_elements.htm
3. If the performance model does not require pressure data, then you can omit the column from the file. See the footnotes in the table in the "Weather Data Elements" help topic for a discussion of when pressure data is required.
Best regards,
Paul.