Let's say yesterday I had a turnip spike, if I TT back to that day will the price still remain similar or it'll change?
actually it depends on whether you are logging back on on the same day, or if you played today and want to tt back. If you have not played at all, you can log in, have isabelle set the time/date to yesterday, and the turnip spike should stay the same. Once you have crossed the 6am line in either direction all prices are reset though.