US Immigration from Ukraine

Hi we are preparing our package I 751 to be send ,I need to know, my husband it's in the title of our home, garranty deed, but not on mortgage because we buy our house just a few months after he enter the country so he wasn't working yet and have not credit score yet. It will be ok sending the garranty deed Showing both of our names? Mortgage is on my name and my older son. Anyone with similar situation.?

Thank you.

Background & Plan:

My fiance with two minor kids lives in her country and I have applied for a K-1 visa recently and received the receipt from USCIS. I know that it's a long wait before the visa petition moves through the different stages and finally gets the visa. Our plan is once she gets the K-1 visa she will come by herself to the US and we get married here and apply for I-485 for her and the kids. Below are my questions and appreciate it if anyone here who has the relevant experience could answer my questions here. Thanks much in advance.

Questions:

1) As she will be coming by herself on the first trip on K-1 visa can I still go ahead and apply for I-485 for her kids along with hers or do the kids have to be present in the US for me to apply for them? If I cannot apply for the kids without them being in the US then what options do I have?

2) As the green card process might take a long time she might need to go back to her country after 2-3 months of stay in the US to take care of the kids till the green cards arrive. I heard that if the applicant leaves the US the applicant's I-485 will be terminated as USCIS will deem the I-485 application is abandoned. What is that I need to do here in such a way that she can travel back to her country and still have the I-485 in motion?

3) In connection with my question in #2 above someone suggested applying for advance parole so that she can travel back to her country. Is that true? If it is true then when I receive the green cards for her and the kids (hoping that I can apply for kids green cards along with her without them being in the US) can I courier them to her country so that she can come back to the US along with the kids?

4) To avoid all the above complications if she plans to come along with the kids on the first trip do I need to apply for K-2 visas for the minor kids now or based on her K-1 visa (kids details are mention in it) she just needs to fill up DS-160 forms for each of the kids before the interview to get the K-2 visas?

I apologize for the long questions but I want to make sure that I do the right thing and not mess up the entire situation. Please answer in the same order so it wouldn't add up to the confusion I'm already in . Thanks much in advance.

I used FedEx next day and USCIS got my package on Oct 8, 2021

On Oct 14th I got this message

USCIS: Your case was received. Receipt #Blablabla Official Receipt Notice (Form I-797) to follow in mail.

Hi I am filing form I 751, my spouse is the petioner we are filing together. I need to know if I his spouse can be his interpreter and also be the person preparing the form?

Thank you.

Who has already passed interview since 1 October from k 1? If i passed medical checkup last October in my country and i have complete about vaccination so do I need take covid vaccine for interview? Mine is in a few days