Custom wordpress loop query for front page w/ infinite scroll and adrotate

Background
* Brand new wordpress theme built on JointsWP, which uses the Foundation 6 framework
* I do not need any styling, just help with a wordpress loop query whilst simultaneously invoking infinite scroll
* I can provide FTP and Wordpress access
* The site is not yet live. It is on the prod domain but is hidden from public view using a coming soon plugin

What’s needed
* A single wordpress loop query for the front-page.php
* The code must be commented sufficiently in english for me to understand it so I can learn
* I may need to take this code and replicate for category pages (alternatively I may come back to you for help

The query
* The front page will have a few elements on it already, so these must be negated from the final query
* Do not show a post with tag id 12
* Offset the query by 2 because these will be shown higher up in the design
* The loop must invoke infinite scroll in the most lightweight method possible
* Infinite scroll preferably not from a third party plugin except if you can get it to work with JetPack or Bill Erickson’s script
* The query must also include a counter or applicable method to inject an advert at position 4

Loop order - see attached jpeg
1. Post 3
2. Post 4
3. Post 5
4. Random ad from ad rotate group
5. Post 6
6. Post 7
7. Contained full width ad from adrotate
- INFINITE SCROLL -
8. Post 8
9. Post 9
10. Post 10
11. Random ad from ad rotate group
12. Post 11
13. Post 12
14. Contained full width ad from adrotate
- INFINITE SCROLL -
15. Post 13
16. Post 14
17. Post 15
18. Random ad from ad rotate group
19. Post 16
20. Post 17
21. Contained full width ad from adrotate


Next steps
Please let me know if this is something you can do. You may need to provide examples of wordpress websites where you have implemented infinite scroll effectively. I will let this ad run for 24 hours before selecting a candidate.

Acceptance
* It works
* It is implemented on the test site
* I understand the code based purely on the comments you have added to the code or you can provide me with a separate written explanation