Redirecting a user to a different home page I am trying to create a site where any logged-in user is redirected to a page that is specific for that user, when the user logs in.

Suppose that U1, U2, U3 are three users on that site. U1's home page should be http://www.example.com/u1; if U1 created any link, the link should be displayed on http://www.example.com/u1, not on http://www.example.com/u2, or http://www.example.com/u3.

I also want different admin panel for each user logging in.
You can do this with a combination of the themekey module and the login destination module. For both, you would start by creating specific user roles for the your three user types, ex


userrole1
userrole2
userrole3


Then setup these two modules and have all users with userrole1 redirect to a specific page after logging in:


  The Login Destination module allows you to customize the destination that a user is redirected to after logging in, registering to the site (7.x), using a one-time login link or logging out (7.x). The destination can be an internal page or an external URL. It is possible to specify certain conditions like referring pages or user roles and make the destination depend upon them.


And then use themekey to switch the theme / output based on the specific user role: 


  ThemeKey allows you to define simple or sophisticated theme-switching rules which allow automatic selection of a theme depending on current path, taxonomy terms, language, node-type, and many, many other properties.