Write a trigger on Opportunity LineItem , when Line Item is deletes, delete an opportunity as well.?

Hi, 

Can we view Salesforce files logged in as Community guest user? I have a file related list under case I can view File related list when logged in as community user however prior to log in (as a guest user) I can see case but not file related list. Are files visible for a guest user? If yes how can I enable? 

Thanks,