giveup wrote: Is there a difference between ‘bootable’ and ‘reinstall’?
Yes. Boot is when you start up a comp from “off.” Bootable is starting up a Mac from a disc by holding down the “c” key.
Reinstall is installing software that was previously installed. You are returning the software to your comp.
Regarding your other questions-concerns, I would suggest that you read the following Knowledge Base Article & website links:
https://support.apple.com/kb/PH18837
How to back up and restore your Mac with Time Machine
Hopefully one if not all of the articles will answer your questions & concerns.
HTH
