How can i list all available default custom properties in the product database? Alternatively i can check them in Custom Properties reference whitepaper but i want to get this complete list in database query. Is this possible?
I don't understand your question. What's available in the postgres database (which is where custom property definitions are stored) and what's referenced in the Custom Properties documentation are not the same thing. Are you asking how to retrieve the ones that have been defined within vRA? Otherwise, the reference documentation has those which are system reserved and possible to use, but it's not like they're hiding out in the DB somewhere.
For this you have log insght's database management pack, you can download it and see the details more easily.