I hope to efile both my federal and state tax. And if I already efile my federal tax with Turbox tax, could I efile my state tax with Turbox tax too
You can e-file a state tax return after the federal tax return has been e-filed and accepted by the IRS.
Yes, if you delete your State return, everything will be deleted. You would have to go back through your State to enter your information again.
How do I e-file my state after I already filed my federal?
I filled that before, but delete that, is there ways to get my previous filling back, or I have to restart and fill everything again?
If you already filed your State return, why do you want to delete it? Once you delete something, there is no getting it back.