Unable to assign front page in WordPress

WordPress front page

This’s the default section in WordPress settings- reading. But to me it’s not displaying. I am getting option from here
Blog pages show at most posts

why it happened ? Thanks for any help

I think it happened because of your WordPress theme. Some WordPress themes have custom page to show blog posts. Switch any other theme and check again.
Is this (screenshot) your current WordPress settings->Reading section?

no. I tried several themes. but no change. this screenshot is taken from wordpress forums, not mine. following is taken from my admin panel.

reading settings

Go to yoursitename.com/wp-admin/update-core.php

choose Re-install now option.

Then check again the problem.

No use. I tried different themes also including twenty thirteen, twenty forteen also. still there’s no such option to set home page.

The front page options on the Settings Reading screen will not display unless you have at least one published WordPress page.