I am using TurboTax Free to file my tax return. At the final step, I was asked to enter billing information. However, I am not Canadian and do not have a Canadian address. The payment amount is $0. What should I do?

Since you’re  not actually paying for anything, you can use any Canadian address, just to allow you to go past this page.

I am not Canadian who returned to my country on May, 2024. I was in Montreal on a working holiday. Can I apply for a tax return online?

You can prepare your tax return online, but you would not be able to use NETFILE to file it. You would have to print and mail your return, or fax it. You can find the right address to send it to on this Canada Revenue Agency (CRA) page: Where to mail your paper T1 return