Moving a 10g database to 11g with rman backup
After alter database open resetlogs upgrade the database should be open.This statement replaces the startup upgrade command.  If this kind of upgrade is possible than you are after the startup upgrade step in the upgrade procedure and you should continue after this step. But you should have prepared the database in the way as described in the steps before startup upgrade. 

I never tried this way to upgrade. You should do this kind upgrade only if you are very experienced with Oracle know exactly what you are doing. Otherwise you should choose an upgrade path that is recommended by oracle like Database Upgrade Assistant or a method like import/export. Check the manual