一定 means in general term " be sure ". But the correct answer was You HAVE to help me... "You Have to" in general term means 不得不。

What is "一定" here for? Does "一定要" mean "to have to; must"?

Do we actually need 要 here, since "You must help me" & "You must WANT to help me" do mean differently to me.

差不多， 可“必要”的意义有“must"或”need to"的感觉，“一定要”更有英语的“certainly will“。

You really must help me

必要和一定要一样吗？

Would "你一定帮我！ " also be correct and mean the same?