Stats appear as if the Pokemon was Level 50. Natures and IVs are taken into account the whole way through. | Source: Experience
For EVs, take how many EVs you have in said stat and divide that by 8. That's the boost in the stat you get. You don't gain any EVs through leveling up to Level 50 through WiFi battles. (So, essentially, EVs are counted as if the Pokemon was Level 50 with the current EVs you have on the Pokemon.). | Source: Experience
if I have a not yet EV trained Pokemon at Level 8 via accidentally leaving it in the daycare too long, will its stats appear as if it had started training at level 8 or level 1?
Level 8, but it does not matter as the Level 50 stats are the same no matter what the Pokemon's level is. You also don't gain any EVs through leveling up in Day Care, as the Day Care raising your Pokemon requires no effort on the Pokemon's part. | Source: Experience