Hi,
I am asking about the reference letter. Do we need to mention education/license etc in that?
Nope.. employment reference letter needs the following
1) job roles and responsibilities
2) employment start date and end date or it must currently still employed.
3) number of hours per week ( should be more than or equal to 40)
4) annual salary or monthly salary ( fixed part only not variables)
5) designation ( all designations held till date)
6) date of issue ( should be current date if it's a current job , if past job, date of issue can be any date after you quit)
Also review IRCC website , I doubt I missed any point.
Apart from this do not add or delete anything else it will result in unwanted complication in your file. Good luck.