US Immigration from Canada

Finally got my interview scheduled under 3-year rule. I'd gotten my 10year green card a few months ago. Wondering, for those who are went in just for the citizenship interview what did they ask you and what documents did you bring? (I'm aware that for those who haven't gotten their 10 year gc, that the interview/approval for that is sometimes done at the same time as the citizenship interview).

I am currently in the process of applying for a K-1 visa, and originally, my fianc 's father was planning to be our joint sponsor. However, due to health issues, he is now unable to work and will undergo heart surgery. Despite this, he does have sufficient income to meet the financial requirements. Does he need to show employment to be able to co-sponsor? Thanks.

The sum of the question is mostly in the title. I understand most questions regarding this process are how to speed it up. However, in my situation I d like the flexibility to slow it down.

My wife would be the USC petitioner. Currently our plan is to relocate to the US at the end of the decade. However, we d like the option space to accelerate that timeline if our plans change. I understand one can draw out the process at the NVC stage by slow rolling fee payment, document submissions, etc. However, using these techniques only, strikes me as buying time limited to about half the period I m looking for. Does anyone have experience or anecdotal evidence that the process can be extended after exhausting these official steps simply with letters to NVC requesting the case be kept active?

Finally, in case the additional context is useful, we d be immigrating from Ontario, Canada.

Finished the most insanely quick and simple interview ever. The consular officer said that she planned to approve me BUT one of her systems was down and she couldn't officially approve until the system was back.

And, that if when the system came up and they need anything else they will "let me know".

Of course I asked for clarification because I am not clear on how I will know once I am official and she was unclear on how long it would take.

She kept my passport and gave me a sheet on how to track my passport/visa.

I asked questions but feel very unclear on how to know if I am officially approved? Will the CEAC site show this?

Still kind of spinning.

I recently got my Green Card. I travelled back to Canada to visit my family. I am heading back to the US in a few days. I am wondering at what point we present the green card when we fly home- I know we present it at customs but do we also have to present it to airline staff when checking in and boarding the plane? Or do we just check in as usual with our foreign passport and just present the GC at customs?