Filling for U.S. Citizenship (N-400)?

You appear eligible for the N600 which is a better option for an already naturalized citizen.

Can an alien person get naturalized citizenship with a general discharge?

He should be able to apply based on the information provided.

Can I still staying in US while My I539 form is still processing and no result?

The wait time has increased due to COVID so you should expect to wait a bit longer. There is no way to know whether your B visa will be approved...

Should I appeal?

You may be able to appeal the decision or file a lawsuit in Federal Court. However, English language proficiency is a requirement for US citizenship.

Yes, you should complete the change of address form to reflect where you actually reside.

Can i change my visitor visa to visa student ?

You would have to arrange an F-1 visa with your school and then file to change status. From the USCIS web site: In general, you may apply to...

Can my sponsored mother get a visa with all the restrictions being put it place?

The April 22, 2020 Presidential Proclamation appears to be applicable in this situation. Does she have a valid visa for entry into the United...

Documents for citizen application and take with me in the interview?

Bring in original copies of all of the documents you sent in with the application. This includes Identification, green cards, birth certificate,...

You have to wait for the decision. Without reviewing your correspondence with the USCIS it is not really possible to know what is going on.

You submitted it in 2018? Yes, that is a bit unusual but you have received the appropriate receipts.