Big bone, nuff said
No they are not and i don't see how that's Pokemon cos ruby gloom is a TV show
light novels are Japanese books, American franchises like Avatar and Ruby Gloom their books are more considered like influenced.
There's many kanto Pokemon in ruby not a whole lot but there's a select few you can capture like rhyhorn, oddish, gloom and many more.
Unfortunately, Gloom is one of those Pokémon that does not evolve by level. If you want Gloom to evolve into Vileplume, you will need to find a Leaf Stone. If you want to make it evolve into Bellossom (which appeared in the second generation (Gold/Silver)) you will need to find a Sun Stone. Also, this is not specific to FireRed, evolution factors are the same through all the different games (though certain pokemon, like Tangela, can only evolve in later versions of the series). For more information, try this site: http://www.serebii.net/pokedex-dp/044.shtml
a rodent skull is the skull of a rodent such as a mouse or a mole or something like that
Diamond is NOT like a ruby.
Then you would have to trade with someone. But if it helps... the only way to get bellossom in-game is to USE a sun stone on gloom, don't have gloom hold it, but use it on gloom (like a potion)
A certain stone that evolves Pokemon like gloom.
ask her out or give her hints
Your skull
It is possible he likes Estelle but that is never proven, and their are hints that Rita might like him but that wasn't proven either but their are hints that he may like both.
You get a guy to ask you out by leaving him hints here and there and sooner or later he will recognize your hints. I won't promise you he will like you back though.