Mom, Thanks a lot for the clear answers.
I called KCC, here is what I gathered:
3. confirming your reply (as well as Mxmlittle's, thanks): Once you select AoS on the first screen, the way to switch to CP (to your home country) is by (1) submitting the form as is (2) email KCC and ask them to make the change. They will. If it's to a 3rd country, they will unlock the form for you to update the address.
4. Confirming your reply, she said it depends on the local office. She advised to call them once FY18 begins to have a sense of the timeline, she mentioned, sometimes [LO] can be 6 months behind, sometimes they can call you for an interview "right away". She finally, advised to 1. switch to CP, 2. once I have, some clarity on the AoS process (by beginning FY18), and I accept their expected timeline 3. switch to AoS.
Thanks again.