Does a study gap, a low CGPA or a weak CV kill my application?

Short answer: Not by itself. A gap is a fact about your history. What matters is whether it is accounted for.

This is decided twice, by two different bodies

1. Your university decides whether to admit you. This is where a CGPA and a CV genuinely weigh, and where a gap is assessed against the course. M8 covers it for master's applicants.
2. The embassy checks that the course fits your background, and that funding and documents hold up (MUR circular). Your admission is evidence that the first body already judged you capable of the course.

What an accounted for gap looks like

You were working, and you can show it. You were caring for family. You were retaking or finishing something. You were saving for this. Each of those is an ordinary life, and an ordinary life explains itself.

What an unaccounted for gap looks like

Several years you cannot describe, next to a course with no relationship to anything before it.

What I do not know

How much weight any of this carries at the visa stage, or whether there is a length of gap at which it becomes a problem in itself. No source says, and I am not going to put a number on it.

The part worth hearing

Students with gaps and modest grades get admitted and get visas. What they have in common is not a trick. It is a file where each part agrees with the others, and a reason for the course that is actually theirs.