My desktop remains empty .. and unable to open terminal in either ways ctrlaltt and t

If you want a terminal and CTRL+ALT+t doesn't open one, try CTRL+ALT+F1 or F2 which should bring a full screen terminal up for you. But first, have you tried setting the Unity 2D option at the login ptompt?

Thanks Barry Drake, that solved my question.

sorry barry drake that doesnt solved my problem ... im very elementry to ubuntu .. moreover pls lemme kno wat is unity 2D option at the login ptompt... hitting ctrl+alt+f1 gives me a blank screen with username and password tried with several attempts seems to b vain... pls post again at ASAP

The blank screen is a terminal. You put in your username and enter, then your password and enter and you get a terminal prompt. I understood that was what you wanted.

To use Unity 2D, you click the Ubuntu symbol to the right of your username on the login screen. This gives you the option to set the default to Unity 2D. Unity 2D will run OK with graphics controllers that can't use Unity 3D.

Manage to login to tty.
https://www.youtube.com/watch?gl=US&v=-LALnzOxsZI

Workaround #3
https://answers.launchpad.net/ubuntu/+source/unity/+question/192477

Seems related to Unity and compiz:

A) if you have autologin not active please choose Unity-2d at login (click on the gear wheel near the user name at login)

B) if you have the user automatic login set (you can't change session preference without login first) so please turn off the automatic login for your user, how to do using terminal:

1) switch to a pseudo terminal by pressing press ctrl+alt+f1 whn the pc is strarted and you have the clear background and made login with your user and password

2) edit the file /etc/lightdm/lightdm.conf to do it type:

sudo nano /etc/lightdm/lightdm.conf

change the row:

autologin-user=yourusername

to

autologin-user=

save and exit then reboot by pressing ctrl +alt + canc or type

sudo reboot

at lightdm login please choose a different session mode foe example unity-2d