Can't talk for Beijing, but I've seen it in CarreFour in Zhuhai and Shenzhen. CarreFour also carry their own brand of this type product. I would not trust the French to be able to imitate such a wonderful product. If you can accept slight variations then it is actually not that hard to make home made nutella, of course your will not get it exactly like Mr Ferrero

Supermarket. Aisle four. Bottom shelf. Four along. Just next to the peanut butter.

(No idea.)

Silva, same question all around 

Beijing Carrefour. Metro line 10, get off at Guomao station. They have Nutella and Reeses chocolate spread.

Jenny Lous and April Gourmet also sell Nutella. I've even seen them sell the white/milk chocolate swirl kind!