The service includes raising your Tailoring skill to the level defined by the selected option. The exact route depends on your current skill, available recipes, and profession requirements.

Yes. If your Tailoring is already partially leveled, the service can continue from your current skill toward the selected target.

That depends on the selected service option. The amount of cloth and other required resources varies by current skill and leveling route, so material conditions should be listed separately.

The main purpose of the service is profession skill progression. Rare recipes and crafting unlocks with separate requirements are not automatically included in standard leveling.