filing questions for mom's GC who is not yet 79.

Here is what I did so far.

I have already filed I-130 on online, got automatic receipt back but not the one (I-797?) with A#,

plan to file I-485, I-131 and I-864 through USPS in the next few days to take advantage of concurrent filing. questions: 

1. In this case, may I still mail in I-131 together with I-485 and I-864?

2. If yes to Q1, as both I-485 and I-131 are required to do medical exam through I-693, $85 should I pay with which form? or twice? 

3. I-485 allows and recommends to file I-693 later even wait till the inteview to bring it in inperson.

"You are NOT required to submit Form I-693 at the time you file your adjustment application, but may do so if you wish. Because of the time-limited validity of Form I-693, you may choose to submit your Form I-693 after you file your Form I-485. You may also submit Form I-693 in person at an interview in a USCIS field office, if an interview is required. By waiting to submit Form I-693, you may avoid having to repeat the immigration medical examination."

But I-131 says 

" After you have filed this application, USCIS will notify you in writing of the time and location for your biometrics services appointment. Failure to appear to be fingerprinted or for other biometrics services may result in a denial of your application."

I have already booked a medical exam apt on 4/1/24, should I cancel it and wait till USCIS inform us when and where to do med exam? Or we can still go on with our apt? Should we bring in an I-693 form? 

4. after med exam, should I mail I-693 in for I-131 or should we hold on it till the interview for I-485? or we'd better to have two copies? Could we?

Thanks a lot,