Thanks for your answer.
No, i didn't amend via Sprintax. I did through Turbotax, as the Turbotax agent herself told me so. This is so disappointing. I didn't have any information and i feel now like being misguided. The agent should've told me not to amend with TurboTax. I have clarified to her whether the apps will make a report for 1040-NR, and she said repeatedly that TurboTax will decide whether it's 1040 or 1040-NR.
I spent money for nothing.
