The factory reset of the handset and setting by hand all email accounts and network/Wi-Fi setting, absolutely no restoring of earlier backup, resolved the battery drainage and the overheat issues. Now the battery holds a day use as before the os upgrade.
The problem fixed! However this meant a lot of manual work! Setting all the email accounts, network settings, screens and apps. Apps were re-installed one-by-one with a help of itunes. The one and only restore in this procedure.
The problem fixed!