I'm looking for information on APFS Snapshots

I’m looking for information on APFS Snapshots:
1/ How to access the protected folders of mounted volumes (snapshots): Data@snap-xxxxxx for mount it in the Finder.
2/ How to get the size of a Snapshot? (eg: com.apple.TimeMachine.2023-02-02-132843.local)

I’m not sure what you want to achieve but you may look in terminal for the command tmutil to list and mount snapshots. See man tmutil

After the snapshot is mounted you can see the sizes via df command, e.g.

df -m
df -h

Thank you for your answer
I already use the ‘tmutil’ command which I know well. Apple no longer allows APFS snapshots to be mounted with the ‘open’ command as was the case under HFS+.
I list them (name, creation date) but I also want to display their size, unmounted.

No idea about the open command but mount should work.
I don’t think that you can get the snapshot size without mounting the volume.