Eligibility
To be eligible, you must
Also, yes it details at the time of the application when digging in more details, the general idea seem to be that you must be currently employed to qualify for this pathway. Since it is the first year and since it is full, I believe it would be a significant risk to go unemployed during the application process. Furthermore they most likely could reach out to your employer at any time (since you had to provide contact information and all) to confirm your employment. I'd say it would be a significant risk, most likely not so much if you just quit for another job that qualifies under the program, but definitely one I would not take lightly if you plan to just go unemployed.
Again, we don't have much to go on with this program, but for most of the other pathways, requirements at the time of application carry over for the duration of the process and only stop when PR is granted (landed), for example financial requirements for PGP list requirements at the time of applying but it is also well known that those financial requirements continue (and increase actually as LICO rises) during the 2 year process.
After that, I guess it all depends on the reason why you want to quit.