Yes, I am applying for my citizenship. One of the questions for calculating physical presene is "During the 5 years of eligibility, have you had a valid status before becoming PR" . My question is what do I respond to this question if I was out of status before I received my PR.
Answer questions honestly, thus as completely and accurately as you can based on your best understanding of the question and the facts.
Since you had student status in 2021, until December you say, you MUST report that (assuming you make your application in the coming months). I am not up-to-date in the application logistics, so I am not sure how it works in terms of entering the start (from) date when that was more than five years ago. The end ("to") date is the date that status expired.
The fact that you were in Canada for a period of time when you did not have status (a period some say was "out-of-status" or others would say was an "overstay") has no direct effect on subsequent status so long as you were not subject to any inadmissibility actions, no removal or departure orders or such (the sort of thing that, if you were, would need to be reported in response to relevant part of prohibitions question).
Subsequent to any overstay or period without status, the obtaining of valid status (such as obtaining PR status; been there, done that myself) cures any previous overstay or period out-of-status.
Caveat: which should be obvious, is that of course this depends on no misrepresentations being made in obtaining status.
I cannot say to what extent a processing agent or officer might take note of the overstay and because of that scrutinize your case more thoroughly. Some officials, probably most, will have some concerns when they are handling a client who has clearly not been following the rules. But so long as there have not been any misrepresentations made, an overstay subsequently cured by obtaining valid status (again, such as PR status) is not at all a big deal. So even if it happens, even if a processing agent or officer takes a closer look at you and your application, the overstay should not have any impact on the outcome.
So . . . again . . .
answer questions honestly, thus as completely and accurately as you can based on your best understanding of the question and the facts.
Didn't you just answer it in the question? "have you had a valid status before becoming PR? I was out of status before I received my PR" If you are out of status that = NOT VALID
You appear to have overlooked the OP's valid student status in 2021:
I did have a valid status for 1 full year as student from 2021 Jan to 2021 December
The fact the OP was subsequently in Canada without status does not change the fact the OP had valid student status during the five year eligibility period. That must be reported.