1) SharePoint Foundation Server and SharePoint Enterprise are the same on the Server side, it's the client licence which determines the version. So not sure exactly what you are trying to simulate, but server-side it would be the same either way.
2) In theory Office Web Apps will allow collaborative editing, but Excel Online is much better at handling it. I would personally discourage using Office Web Apps as Microsoft is pushing us all into SharePoint Online so I am not sure how much more work will be done to the non-Online versions.
3) Outlook 365? Do you mean Office 365? If so, you will find that "SharePoint Online" aka office 365 (depending on what Licence you sign up to) will do the client-side things that SharePoint 2013 does but you will not have access to server-side code such as DLLs written in C# etc. You have to do everything with Javascript and the JSOM code. That is the way Microsoft is pushing everything, so if you are trying to "learn" Sharepoint that would be the way to go, especially as it gives you transferable skills outside the SharePoint silo.