Hi its clear......
When they update second line they will actually start processing.....
2 line (without third line decision made) means u passed eligibility.... both minimum requirement and 67 points..
Now, after second line, though u passed eligibility, a officer may have questions about three things
1) some of ur documents could be suspicious to the officer (like exact match of job description) then the officer will ask the other officer for second review
2) may be they wanna do ur employer verification... then they will go for background checks
3)officer can have questions about ur abilities or need clarification about something from u..... INTERVIEW CALL
AT THIS STAGE, 2nd line and no third line decision made, they cannot reject u directly.... they must give u an opportunity to explain ur self or to provide further proof of docs....
If an applicant successfully finishes this stage.... eligibility pass........
Now MR....
So time between 2nd line and MR is the time they MAY perform ur employer check... if and only if they want to...