first of all how do you get dive in the first place?
Use your poke flute in your pokegear where the radio is
you need to have the EXPN card once you have that, go to vermillion city and use your radio on your pokeradar to wake it up.
Red is another name for Ash Kectum
any water Pokemon can use dive
You need to get the HM dive from Steven in Mossdeep City. Then you will have to beat the gym leader in Mossdeep City. Then you will be able to use the HM dive. And you find the dark spots in water while surfing. Use dive. And to resurface. Use dive again!
cerulean cave Pokemonheartgold/soulsilver catch him with a dusk ball (easier)
No, you can only capture it in PokemonHeartGold ,Platnium,Diamond and Pearl!
you need to use a water type pokemon and teach it dive or use action replay
Only one, but I'm sure there's ways of winning it too.
When you Surf, you will see dark spots in the sea. You can then use Dive, and go underwater.
simpliy the dark spot leading to sootopolis you have to use dive
Since dive is not a HM in firered you will have to trade a Pokemon to a friend that has ruby, sapphire or emerald then using that game use the HM Dive to teach the move Dive to that Pokemon trade it back so firered can have that Pokemon again it will still have Dive however you cannot use it to dive underwater.