The forms are available through the Tous Anti-Covid19 smartphone app, or else via the government’s website
Yes, you are allowed to move house, but the removal company needs to provide you with an attestation. I’m not sure what kind of attestation you would use if you moving house on your own (or with friends, etc).
Yes, you can collect a car from a car sales establishment. They will appoint a time and place for pick up and ensure the strict health protocol is applied. You will not be able to move about within the car showroom though (this very question was asked on France Info this morning).
International travel is not banned, but it is strictly monitored. In some cases, depending on where you are entering or leaving the country, and your destination, you will be either subjected to an antigen test (entry via French airports) or else may have to provide a negative RT-PCR test that is not more than 72hours old.