If you have eight badges, it's easy. Just go to Viridian City (The first city you visited) and head west.
you fill your pokedex
you need to catch it first in fire red/ leaf green and migrate it to pearl after you beat the Pokemon league.
you cannot rent any Pokemon in red version
Yes, Pokemon Sapphire version is the version in which you can catch Latias. You can only find it once you have beaten the Pokemon League, then there is a report of a legendary red flying Pokemon in Hoenn. Latias appears randomly.
rock smash isn't in Pokemon red version
You Can Go Into This Cave Once You Have Beaten The Pokemon League. Cerulean Cave Is Where Chanseys And Mewto At LVL 70.
No
the Pokemon league is is in ever grande city after you get through victory road
defeat the Elite Four at the indigo league
let all you're Pokemon faint and you'll return to the last Pokemon center you used.
You can't, you can only do that on Pokemon yellow version
Next to Cerulean City. You must have beaten the Pokemon League, and have restored power to the trade thingy on One Island to get in.