On: every psalm and song in the daily prayers uses today’s English. Off: all of them use the older “thee and thou”. Until you choose, the Songs of Zechariah, Mary and Simeon use today’s English, as most churches sing them. The Lord’s Prayer and the prayers for the dying show the form most people learned.
Turning back. In Lutheran teaching it has two parts: contrition, which the law produces, and faith, which the gospel produces. Not primarily a feeling of remorse.
In Doctrine — What Lutherans teach, and where it differs from neighbouring traditions.