L'Chvod Rabbi Shapiro, Shlita:
1) Is visiting the grave of a deceased parent on the Yartzeit, beneficial for the parent's Nishama?
2) Is visiting the grave of a deceased parent on the Yartzeit, an obligation or a custom?
3) Can a person visit the grave within a week before the Yartzeit, or within a week after the Yartzeit, and still fulfill the obligation / custom,
especially if the Yartzeit comes out on Shabbos or Yom Tov,
or if, for some other reason, the child can't visit the grave on the Yartzeit date?