1. Can I catch a syther in Red version?
Yes. In fact, Scyther is a Red-exclusive Pokemon. As in, between Red and Blue, it's only available on Red.
You'll be able to find them in the Safari Zone, particularly the first area you're in, if I recall correctly. You may be looking for awhile; Scyther tends to be rare, even there.
2. what fire or electric pokemon should I get later in the game?
If you don't start with Charmander (which would get you Charizard, possibly the best Fire-type besides Moltres), Arcanine is probably your better bet. You can get them as Growlithe as early as the route east of Celadon City, and be careful because they know Roar. Alternatively, you can find them in the Pokemon Mansion on Cinnabar Island. There's also Moltres (in Victory Road), although I personally prefer not using legendaries myself. *shrug*
As for Electric-types, I personally prefer Raichu because you can easily raise one from a Pikachu you get in Viridian Forest or from the ones you get in the Power Plant. Voltorb/Electrode (which can be found as early as just north of the Rock Tunnel but can also be found in the Power Plant) are also incredibly fast, so you could be dealing hits before the opponent can even move. And if you don't mind using legendaries, there's always Zapdos.
