Byline is just your name as you would like it to appear with your writing. For example, Jane Smith, or Dave Jones, Ph.D., etc... TRhe reaosn they ask this is some people like to be called Barb, but want their byline to be Barbara for instance.

Author bio depends on the publication. The one I work for wants to know position, school you work for, city, state, and contact info.

For this devotional thing I would put your city, address. What you do for a living. Kids, husband, and maybe one sentence on your faith that intersts you.