Hi Nikunj,
Best method to debug your query (as it's having 4 queries combined using Union ALL), is to try including one query at a time without any command level filtering using prompts.
If the query is giving some data, then try adding your prompts one by one and execute the report each time to make sure you are getting some data for the prompts you are including.
Say one query is perfect and giving output with all prompts. Then try the same steps for other queries also.
If everything goes well, try combining them using Union ALL.
If individual queries are giving output, then your combined query (using Union ALL) will also have data even if one of your queries is retrieving some data.
Hope you will get some hint on how to proceed.
Thanks,
Raghavendra