I have installed flash player in my PC but its not working in "HOTSTAR app for windows 10" it always ask for installation and updation
Flash Player on Windows 10 is a built-in component of IE and Edge. There is not a separate plug-in to install or download.
Before Windows 8, some applications would look for and use the ActiveX Flash Player installed on the system for Internet Explorer; however, that doesn't work in Windows 8 and higher because of architectural changes made by Microsoft to their browser and operating system.
I can't say for sure that this is what's happening because I don't work on Hotstar, but it seems like a possibility. My recommendation would be to contact them directly for support on their application.
How can I contact them directly?
A quick search for "Hotstar support" should get you what you need. Their site is geo-restricted, so I can't see much.