See what score change a grade appeal needs.
An appeal is worth the effort only when the marks in dispute can actually change the outcome. Convert the boundary you want into raw marks, subtract what you were awarded, and you have the minimum the appeal must win. Compare that against the marks you are genuinely disputing: if the disputed total is smaller, even a completely successful appeal leaves the grade unchanged. This is the calculation to do before writing the submission, because most institutions allow one appeal per assessment and remarking can move a mark in either direction.
Marks an appeal must win
Marks needed = boundary % x total marks / 100 - marks awarded
Procedural irregularity, a marking error such as an arithmetic slip or an unmarked answer, or a demonstrable departure from the published rubric. Disagreeing with academic judgement is not usually grounds on its own.
At many institutions, yes — a full remark replaces the original mark in both directions. Check whether your regulations guarantee the original as a floor before requesting one.
Only near a boundary. If the marks needed figure is 0.5 and you are disputing two marks, the appeal is decisive; if you need eight marks and dispute one, the effort will not change the grade.