Blue Questions

So every time I login it sends you a code to email. So there is no login and password?

Do tasks and events from multiple companies/workspaces show on the master calendar and task view on the sidebar? Or does each workspace have an individual calendar for events? It would be great if everything syncs to the master calendar (do we don't overbook ourselves when working for different organizations)

Let's say that I refer BLUE to an associate either as a LTD or paid plan. If they create their own account and Company, and they add me as a user to a project, will that Company/Workspace seamlessly show in my workspace/company dropdown list? I won't be an admin on that workspace - just a guest user, but will I be able to switch to that project from my normal login?
Or will the associate experience an error when trying to add me to one of their projects because the email account already exists in the system.

I try Blue this week and it really give me best experience using Project Management Software, after the trials end, can i continue upgrading using AppSumo LTD? Thank you!