Do I have to buy my own domain and what is alibaba cloud url?

Is the domain name provided by Alibaba Cloud or do we have to buy and arrange for it.

You have to develop the application on
your local system and submit the
Alibaba Cloud URL where you have
hosted it

What is the Alibaba Cloud URL?

No, domain is not provided by Alibaba Cloud. You would have to arrange it on your own.

This is alibaba cloud url :

By arrange do you mean we will have to buy a domain name?
Is it necessary for hackathon?

Yes, by arrange I mean buying a domain, if you want to. If you are not using a domain, then you and your users will have have to make calls to the public IP of your Alibaba cloud instance.