Is this engagement ring real?

Well it says on the site that the gemstones are cubic zirconia, so no, not real diamond. Cubic zirconia is a cheaper diamond substitute made from a completely different substance. The only way I could see to test the silver is to wear the ring. If it were real sterling silver and since the ring isn't plated as far as the site says, it would leave green marks on your skin. (It's a myth that only fake rings leave green marks.)