You don't need to show the back of the photo for online applications.
1. It may, but very unlikely.
2. Yes, you'd better.
3. It won't replace, the officer will be able to see what you have sent via the webform.
No major problem at all if you complied with your exclusion order. Your case is quite straightforward and will not cause any serious issues to get a PR.
The company's address has nothing to do with "City/Town where activity took place (required)." You need to indicate where you actually were while working. Sorry I have nothing more to add to this. Wait for some other inputs.