Hi,
I'm filling form 843, because Medicare and Social security taxes were erroneously withheld by my employer. I worked as a J-1 student in 2014.

What address do I have to fill? Does it have to be an address in the USA or can I fill address from abroad (in Europe)?

What should I check on line 6 (Original return) as a J-1 visa holder? I have found that F-1 students should check option "941". Should I check the same option?

If IRS approves my refund, how do I get the money? Do they send me a check to the address I filled?

Thank you very much!

Yes, check Form 941.

You CAN file from Europe, and you can put your European address. They will mail the refund check to that address.

Be prepared to wait. Before the budget cuts, such reviews typically took 6-12 months. Now, it could take 1-2 YEARS.