Hi, I am wonder if I can see all task across multiple project - bord / caendar / timeline view.
Welcome to the forum.
Absolutely, you can view all tasks across multiple projects, board, etc… as long as you have access to them.
Take a look at this how to: Using search & advanced search in Asana | Product guide • Asana
What would be interesting is to identify the reason you want to view all of these tasks in one go.
Hope this helps!
In addition to what @Rashad_Issa said, not all layouts are available in the search results/reports. The Timeline for example isn’t (yet?)