We have an on premise instance of developer portal and we are directly working on the Apigee_Responsive theme given by Apigee. Is it okay to work on this or do i need to create sub theme.
Kindly suggest about the same.
You should create a sub-theme, as described here.
If you want to write custom theme code, do not modify the portal's default theme files. If you do modify a default theme file, then those changes will be overwritten the next time you upgrade your portal.
Instead, create a sub-theme of the theme that you want to modify as described below in the section "
Customizing a theme by creating a sub-theme".