If a Peruvian wants to visit Lhasa, or Hong Kong, does he need a double entry or single entry visa?

If you come to HK for visiting purpose, you will get 30 days free entry with your valid Peruvian passport. So you just need to apply for a single one for visiting Tibet. But you should know that individual foreigners are not allowed to visit Tibet alone. And they should get the Tibet Travel Permit and join a group tour arranged by qualified Chinese tour agencies.