Lamb loin is thin, and the fat you are talking about is a layer of oil wrapped around the kidney.
Roasted lamb tenderloin can be cooked according to personal taste, just like steak in western food. It's up to you whether it's medium rare or medium rare.
Some people like to eat medium-rare, even medium-rare, dripping with blood. Most people can't stand it.
The scientific name of sheep testicles, that is, sheep eggs, is only available to Sao rams, and generally no one eats them. . .
Xinjiang mutton sheep are generally lambs that are not in estrus for about one year old, called sheep wazi, and no one wants to eat old sheep.