It was a very silly mistake of mine. I am now at village for EID vacation and yesterday I was getting very slow speed with GrameenPhone. For some maintenance task, I thought to access the cPanel with my mobile. While accessing the "Legacy File Manager" of cPanel I touched a wrong menu unintentionally and the destruction happened.
To configure firewall as a system admin or even as a normal computer user we need to know the port numbers which will remain open.
Here is a list of common port numbers of some common services.
The issue arises because we may not need the same permission for the files as like the directories. Take a website as example. Generally website files have 644 permission and directories have 755 permission.
Here you can change your permalinks as you like and make it SEO friendly. You will find here 4 predefined permalink structure. You can set them. There's also a box called Custom, You can define your own permalink structure here.