RMAN backup is stuck/taking a long time
Don't specify two conflicting FORMATs (you have one in the ALLOCATE CHANNEL command and one in the BACKUP command).

If and when you need different FORMATs (e.g. one for database datafile backups, one for archivelog backups and one for controlfile backups) specify them explicitly with the BACKUP command.

Eg: 

&gt; rman target mydatabase

    shutdown;
    startup mount;
RUN {
      ALLOCATE CHANNEL ch1 TYPE 
        DISK FORMAT 'C:\Backup_Folder\mydatabase%d_DB_%u_%s_%p'; 
      BACKUP DATABASE;
      RELEASE CHANNEL ch1;
    }
    EXIT;


Note: I noticed that you provided the path starting with "C:/". Shouldn't it start with "C:\"?