US Immigration from Vietnam

I am currently in the process of preparing to help my wife out fill out her AOS/Greencard (I-485) application along with the Work EAD Permit and Travel Docs applications and have a few concerns and questions.

1. What kind of questions do they usually ask?
2. Do both you and your spouse go in together for the interview?
3. How long is the interview process and do they have translators available if needed, my wife's english isn't good?
4. Do they require you to prove that your marriage is real by asking to see a bank account with both your names on it, monthly statements or bills with our names on it, etc?
5. I have a joint-sponsor to help me with the I-864 application, if that person is retired can they still be my joint-sponsor since I do not meet the 125% poverty income rate? My household size is 3 or 4.
6. How long does the entire process take in order for my wife to receive her greencard?

Thanks in advance!

is there example of invitation letter??? My wife want her parents come visit us and our sons for 6 months. Please advice thank.

I recently filled out the i-134 as my fianc will have her K1 interview Next month. As I was on video call with her I showed her the form so we can cross check and she mentioned Page 8, Part #4. I'm pretty sure I leave this blank as it states that portion is if she fills it out on her own behalf. She further mentions to me that people who have recently passed their K1 interview completed part 4 of the i-134. I've highlighted on the screenshot here, any thoughts?

ps: I'm thinking that if I complete part 4, I'll have to change the checkmark on page 1 that states "filing on own behalf" which is not right for our K1.

My wife is applying for her greencard (I-485), Travel Docs (I-131) and Work Permit EAD all at once. But she is stuck on Part 2 Application Type (I-131). She chose 1d so that if there's an emergency back in Vietnam such as a family health crisis or similar, she can travel to Vietnam, take care of what she needs to and be able to return back to the US without any problems. Has she chosen the correct choice? There's also a reentry permit as well. I just want to make sure before submitting the application. Also, regarding Part 3, does this need to be filled out now? She doesn't have a timeframe in mind on when she needs to travel since this all depends on if there's a family emergency, then she will know the date and time for travel, but as of now, there's no need. So can she leave part 3 blank and skip it?

My fianc 's interview appointment is a April 21 and I will be gathering and sending my W-2 form, 1040, and monthly bank summaries; what other documents would I need?

How far back of bank summaries should I include? (how many months?)

How many years of tax returns should I include? I plan to include both my 2022 and 2021, is that sufficient?

Since my fianc 's interview is past the April 15 tax date; will the consulate require the 2022 tax returns, or will 2021 tax returns be ok? I have my 2022 tax returns, but my brother who is is my joint sponsor will file for tax extension and will file taxes in June instead of April, can we use my brother's 2021 tax returns?

I wasn't able to find much about the i-134 here on VJ, except an I-134 example PDF that was from 2018, any tips or links would be helpful. Thanks in advance