as per document billing account user can do only following option https://cloud.google.com/iam/docs/understanding-roles
but as a billing account user i am able to view all resources and create VM instance. how come it is possible
This is a great question, Bala, and it’s very good that you’re wondering about this!
The reason for what you’ve noticed is the distinction between billing accounts and projects–something I cover in more detail in this "Billing Access Control" lecture, just a few lectures further on in the course. 🙂 Please continue watching until that lecture–and if that doesn’t fully answer your question, then please do let me know by posting a new question attached to that lecture! (That way I’ll get a notification of your question.)