How to get Core file or core details from QKview file?

Not sure what you're asking here. qkview files are stored as /var/tmp/.tgz if you generated it from the command line, or case_number__support_file.tar.gz if you used the gui. If you have uploaded it to iHealth, you view CPU statistics from there, under graphs. However, you can see CPU graphs from the Configuration Utility on the BigIP itself: Overview / Performance / System CPU Usage.

If that doesn't answer your question, perhaps you could try rephrasing it.