Questions about HD map annotations

[BMRETURN]

1. In the dataset link given, it seems that only the maplm_v0.1_small compressed package contains annotation information, and the rest of the samples are not annotated.
2. What do the numbers and "geom" in the annotations mean?
3. Where can I see detailed information about the collection parameters?
4. Where can I learn about the principles and processes of generating HD Map Data?
5. Where can I get the raw image data of the HD Map, such as the left half of Figure 3 in the paper?