Is the degree conferral date the same as the completion of degree requirements date? I am an MSc student in Greece, and this year I am applying  to PhD programs in US universities. My question is about my BSc degree.
Most universities require a conferral date as well as a start and an end date.
The start date is the date I was registered.
The end date is Jan 2020.
Now, my BSc transcripts state that I have completed my studies but I have not attended the graduation ceremony yet. The examination period (Jan 2020) during which I completed them is also mentioned. Furthermore, the date the last exam result was announced is mentioned as well - that is, the last course grade (that result was announced after January). Finally, I don't have the degree certificate yet, because no graduation ceremonies have taken place due to COVID-19.
Is completing my studies equivalent to being a graduate or to being conferred/awarded a degree?
I am worried that if I state that I have earned my degree, I will be required to provide the degree certificate (which I don't have yet) and that my transcripts won't be enough. Should I state that I am expected to earn a degree and leave the expected conferral date blank, or that I have indeed earned my degree, and give the date I fulfilled the requirements as the conferral date?
Is the degree conferral date the same as the completion of degree requirements date?

No, not necessarily. Most schools award degrees once per term (whether that's semester, or quarter). So if your last final was on the 8th, you would have received your degree on the same day as your friend whose last final was on the 10th.

Is completing my studies equivalent to being a graduate or to being conferred/awarded a degree?

Again, not necessarily. In most places, you have to &quot;apply&quot; to graduate or similar, which as I mentioned in the comments is the formal check you completed the requirements. This means &quot;completing&quot; your studies doesn't mean anything until you've asked the university &quot;I've done all these courses, can I have my degree now?&quot;
For example, you could have done enough coursework to earn two separate degrees, but if you only apply for one, you only get one.
This very well could be different in some places (or for other types of degree). But it is certainly not a rule to rely on.

I am worried that if I state that I have earned my degree, I will be required to provide the degree certificate (which I don't have yet) and that my transcripts won't be enough.

Nobody needs the certificate in the US, the (sealed, official) transcript will tell them whether you have a degree. If that doesn't say you have a degree, then they won't ask for a certificate, they will think you don't have a degree.
It sounds like there is a possibility you weren't conferred with your degree, because of COVID. You will have to follow up with your university to verify.