Is wearing a flag patch on a backpack against regulations?

No

In this day we should be glad to see anyone display the flag in any respectful manner.

This flag is showing as being flown

PFC Parker, backpack with flag or pach are against AR670-1. Chapter 3, paragraph 3-7. Required or prohibited wearing of the Army uniform. Paragraph f. Bags, handbags, purses and backpacks are authorized, but must adhere to the following criteria: (2) if Soldiers choose to wear a shoulder bag while in uniform, the bag must be black or match the camouflage pattern uniform being worn, and may not have any commercial logos. DA Pam 670-1, 25 May 2017 also give you guidance, the rule change as I recall all backpacks must be black or same as your uniform and no flag or pach was authorized. Hope this will help you Airborne

A pack is not part of your uniform, it's part of your 782 gear.

I don't think so

No

IDK...

Army Infantry 1964-1970. We never wore a patch on a back pack and the subject never came up.

No