US Immigration from Kenya

Am filling form i -134 and a question to fill USCIS online account number is here. Is it the sane as the receipt number because that's the only number I see in my USCIS account.

I have a USCIS account because I have filled i-130 for my wife, we received our no1 and online access code so opened an account with USCIS.

A parent has a valid American B1/B2 visa. They wish to take their child for medical treatment in the US, a procedure that isn't available in the home country. They already know the cost and have money to cover it fully. Does the parent need a Medical visa?

I will be sponsoring my wife for a trip to visit me in the USA, Is an invitation letter necessary? And what documents do I need to show that I will sponsor her? She has already applied for the tourist visa and is scheduled for an interview.

Help me out

We want to try get a B2 visa for my wife to visit me in USA since the wait is long.

I will pay for her airplane tickets and all her expanses. Do I need to fill form 1-134 and where should I submit it or I should fill and then send it to her so that she can have it on her interview day.

To show family ties in her home country should she carry ID cards for parents and siblings.

Currently she is unemployed so we won't have that as proof of her intent to go back to her home country.

In the instructions USCIS says you should type or print none if your response to a numerical answer is zero or none. I have no alien number,the PDF does not allow I type none.

Should I write none with a black pen after I print the form?

Am using the PDF they recommend in the instructions.