That looks fairly legit to me. The only questionable thing is the keychain... none seems to be there.
Fake Tamagotchi do not have the Bandai logo, don't say "Tamagotchi Connection" (or Connexion, as the case might be), don't have the Tamagotchi logo (even though some do, just multicoloured). Know what the latest version is so you know that anything past that is automatically fake.
That Tamagotchi V4.5 is a real one. It is a very common design to, it's called the 'Red Butterflies' design. I would buy it if i was you, but i like buying mine from a shop, not e-bay. But it is up to you!
Hope i helped, and have a great tama-talking day!!!
I live in Holland and you can not buy it over here (not even a V4 ) So my only option is to buy it on Ebay. Most of the time the shipping costs are very high, but at this advertisment it's not that high. I can get this Tama for the same price (incl. shippingcosts) as I bought my V3 in Holland