Im an Australian Resident. Can i change a b1/b2 visa to J1 when im already in the US?

You may change your status from B1/B2 to other nonimmigrant visa like J if your situation comes to that.

I submitted my I-485 and I-130 already. i have receipt numbers already. my question is, will it be ok to show this case status?

Border patrol meaning you intend to travel? If you want to travel, you can apply for I-131. This allows you to take brief trips outside the United...

You will need to deal with inadmissibility issue. Assuming you have been unlawfully present for more than a year, you cannot re-enter for 10 years....

I filled a i360 as widower of a us citizens and did the biometrics in fact I just received my combo card for EAD but

I agree.

Can I send in my N-400 already, while my I-751 is still pending?

If you have been a permanent resident dor 3 years, you may file n400 while i751 is still pending as long as you are still with your spouse.

After being married to an american in the country can a foreign national legally remain in the country?

it depends on a visa the foreigner used to enter. Assuming 1) the visa allows adjustment of status, and 2) the foreigner entered with a...

Is a 1983 Green card still valid?

I agree. It is still valid.

Can i get EAD on H4 visa?

No. H4 cannot work.

Do I need to submit my medical record along with I-130, I-485, and I-765?

I agree. You are not sending your regular medical record. You need to see a civil surgeon listed on the USCIS website. The USCIS officer must...

GC through marriage, when employer based EAD already present?

From your fact, I assume you already submitted I-485 (pending EB2?). I assume you had an attorney who assisted you in filing EB2. Consult with that...