PL/SQL is a process running on the database server. It doesn't have access to a client machine and isn't able to make reports pop up on client machines. It is up to the client application (whether that's written in Oracle Forms, Apex, .NET, Java or whatever) to call up the report from the front end. Don't expect back end processes to push reports to people's screens (unless you really expect your servers to breach all security concepts across the network).
Not true, you can call it, but you cannot display the report, only write it to a file.
You can use the srw package for this Re: run a report from PL/SQL
OR Event driven Publishing Re: run a report from PL/SQL
Or a distribution file
19.5 Distribution XML File Examples