my ubuntu on virtual machine is not undergoing through rebooting after installation, neither it is asking for username and password nor I can write or do something
which virtual machine are you using?
I think your virtual machine is crashed try reinstalling ubuntu after deleting previous ones
Can you please share a small screen recording video of what you are trying to do?
You can use a lightweight tool called Loom to record your entire screen.
Here is a Chrome plugin for the same: https://chrome.google.com/webstore/detail/loom-video-recorder-scree/liecbddmkiiihnedobmlmillhodjkdmb
May be your virtual machine is not updated, please check for update and also you can see on google to how to check for update.