knowledge - First Gym: Brock! Who's this Pokémon?

This question is the second one in a series of Poké-related questions I hope that I can ask.

Who's this Pokémon that:

1. Was (already?) released by the time the generation that has almost as many Pokémon as the number a byte can hold, was released.


2. Has the same name as what was the major event on a Disney Princess's Birthday, in a cartoon movie.


3. The movie was released at the same year as the one I got into Uni, listed in Greece list in my Travel, in the place that Arsenal is notorious for. Indexing for that may, or may not be, the reverse of what one would expect. You can check the year I was born to determine if indixing starts from the start of the list or from the end.


4. Brock has a hard time deciding if he has the advantage or the disadvantage over it!

Answer

I'm pretty sure it's

Lanturn

Clue 1

Generation 2 had 251 total Pokémon (100 new Pokémon combined with Generation 1's 151), almost 255

Clue 2

Rapunzel's parents (and the rest of the kingdom) release lanterns on her birthday each year in Tangled

Clue 3

Arsenal is mocked for usually terminating in 4th position. In your list, the 4th element from the end is an island that was visited in 2010 – the same year Tangled was released (though interestingly not in Greece, where it wasn't released until January of 2011). It could not be indexed from the start, because that destination was visited in 1995, and you were too young to be in university.

Clue 4

Lanturn is weak to Ground type moves (which many Rock type Pokémon have access to), but Brock's Rock types are weak to Lanturn's Water moves