sheena - To unlock HR Schema in Oracle 12c Database, follow the steps below,

Login as sys dba. (use windows command prompt)
sqlplus sys/Oracle_1@pdborcl as sysdba;
Now, you need to alter the database to open the schema available in database.
alter database open;
Now unlock the hr schema.
alter user hr identified by hr account unlock;
Now connect to hr.
connect hr/hr@pdborcl.
Feel free to ask any doubts regarding sql queries.

albert9 - I think you need a comprehensive oracle schema tool to help you do this faster and save time. You can learn more about oracle's schema compare tool https://www.devart.com/dbforge/oracle/schemacompare/ on the site. You can also get started with a free trial and already save time that you might have spent backing up your databases.