A:AnswerIf you are asking about the ability to add a 3rd party add-on then the answer is yes. If you mean other Software on your Operating System then the answer is also yes.
A:AnswerThe annual renewal cost is the standard price of whichever version of Office 365 you choose. If you find it on sale you can always purchase it and add it to your account to extend the subscription. You can learn how to add time to your subscription here: https://aka.ms/AA5opd6
A:AnswerYour Office 365 Business Premium subscription allows up to 300 users. One license covers fully-installed Office apps on 5 phones, 5 tablets, and 5 PCs or Macs per user.
A:AnswerMany services like dropbox, google drive, etc. or backup services charge 15-20/month alone. With the MSFT business account, you don't need any of that plus you get many more features like Teams, Sharepoint, and exchange as well as the office apps. Honestly this is one of the most aggressive pricing strategies I have seen from Microsoft in a very long time.