US Immigration from Sri Lanka

Hi, I am a US citizen father, and my two kids are born abroad. we have gone through the I-130 process and as soon we came to USA I applied kids US passports. and both kids received their US passports.

Now I am trying to fill the N-600 form for kids and its asking a question

Have you ever been a lawful permanent resident (LPR)?

What do I have to answer to this question? coz they never received a green card and we didn't pay green card fees. But their foreign passport has I-551 stamp. Is this means they are LPR ?

We have gone through I-130 process and just got the visa for wife and two kids.

(below 18 years old) they have I-551 stamp on their foreign passports.
Question is how do I apply certificate of citizenship for my two kids ?
What process involved ?

As a sponsor how much income we need show according to poverty guidelines (as a percentage )?

I would like to enroll my two children to a high rated elementary school in my school district.

Can we select the school we want to enroll them in ? The closest one is not rated good.

Hello, my father entered USA with the immigration visa (IR5) a few days ago. He has the passport sealed by the immigration folks at the airport, no issues. My poor mom still didn't get her visa (due to the issues mentioned here):

So she is all alone back in Sri Lanka. My dad entered the US only because he had to before Nov 30th according to the visa restriction.

My father wants to travel back to SL to help my mother get her visa as soon as possible. They are sure she is at the last leg of her visa process (lots of effort going on to get her issues resolved).

My question is, can he travel now? He doesn't have a physical green card. All he has is the seal on the passport. He has only been here in the US for about a week.