steven has to be found in the museoum in peweter city an trade pokemon with him at saffron city
You can get latios after you meet Steven, and latias through the enigma stone event.
in pewter city
You meet Lance in Pokemon SoulSilver at the Lake of Rage, where he is investigating strange disturbances in the Pokemon, after you catch or defeat Shiny Red Gyrados, you and him team up and defeat the Team Rocket group who is hiding in the "Souvenier Shop".
meet blue, the gymleader on cinnabar island
No. The only 2 regions you can go to in Heart Gold and Soul Silver are the Johto and Kanto regions. However, you do meet Steven twice and obtain a Hoenn starter Pokemon. Also, you can find Latios/Latias as roaming Pokemon after meeting Steven for the first time.(Soul Silver=Latios, Heart Gold=Latias.)
7
His house in mossdeep city.
first you deafeat the 7th gym then meet him at the space center
in the cave where you meet steven to give him the letter you need to use rocksmash in there
There are no other encounters with Red in Pokemon SoulSilver and HeartGold than on Mt. Silver. His role is minor in the new Johto games without any dialogue or backstory explained.
on the second gyms island the cave that you meet Steven, the hiker at the beginning will give it to you
You can't. But you can meet red in Pokemon crystal silver gold heartgold and soulsilver. he looks just like him. And of course you can be someone like him in Pokemon yellow red blue fire red an leaf green.