Heading 4105 covers sheep and lamb skins only tanned or crusted — not yet further prepared. Once the skin has undergone additional finishing (dyeing, buffing, surface coating, etc.), it moves to heading 4112. The key test is whether any post-crust finishing operation has been performed; if so, 4112 applies.

Yes. The heading text explicitly includes parchment-dressed leather of sheep and lamb origin. Parchment dressing is a traditional finishing method using alum or oil rather than conventional tanning agents, and the resulting material — if wool-off and further prepared — falls within 4112 rather than in the raw or crust-skin headings.