What determines validity of health/criminal checks?

My COPR is going to expire on 8/2 and I’m going to have to wait a bit more before moving to Canada due to ripples from Covid.

I reached out to IRCC via the web form and got the message with

…We have received your request to extend the duration within which you can confirm your status as a
permanent resident. Please be assured that your application will not be refused if you are unable or
unwilling to travel as a result of the COVID-19 pandemic…

Also came across the [Permanent residence: COVID-19 program delivery] (https://www.canada.ca/en/immigration-refugees-citizenship/corporate/publications-manuals/operational-bulletins-manuals/service-delivery/coronavirus/permanent-residence.html) page which states:
Once the applicant informs IRCC via the Web form that they are **able to travel** , a re-opened application may be re-approved provided that the applicant and their family members, whether accompanying or not, have valid immigration medical examinations, criminal and security checks and passports.

However I’m not sure what having a valid immigration medical examination, criminal/security check means?

Did anyone move to Canada after their first COPR expired? Would love to know what entails after you let IRCC know you are ready to move