You should consider translating the question to have a greater chance of response.

Can I hold citizenship for three different countries?

The United States only recognize one citizenship, the USC. The US does not recognize multiple citizenship. That will be up to your country of origin.

Filing form I-485 for my children..which option I should select in PART 10?

You are signing the application on behalf of the child, so 1a. if you can read and write English.

Would filing I-130 affect getting OPT?

There are two different processes. You should be able to get OPT under F1. Make sure you don't violate any F1 visa status

Can I be forced to refinance?

If you cant refinance, they may try to force a sale.

Can a newborn enter the US with either parent or does it have to be with the primary applicant of the DV lottery?

This is an immigrantion question. I changed it so someone from immigration can answer.

He will have to pay the bill. Check with the ambulance company for a payment plan or reduction

Would she have any criminal penalties?

That's hard to tell. You should get the credit report to see if any judgements against her.

Can I set up a business in the US if am not a US citizen but lives in the US.

You forgot to mention your current status. That is important. If you are here with a visitors visa, you cant work.

Inadmissibility waiver ?

You should consult with an attorney before you do much else. You may not need a waiver but it's hard to tell base on the information you providing.