Remote to a remote oracle server and get running instances?
Agree with first responder.  The only way to do what you want, and not 100% sure it is possible, would be to have very high level permissions on all servers, or have special permission settings.  Any system admin would be justified in asking for any order to set something like this up in writing.  The same goes for the DBAs for the DBs you want to run "sql script in each instance", without user/password signon.  My advice is you need to find a way that works with the standard server/DB security, and stop finding a way around them.