They're in Magma Cavern (a part of story) and you'll need a friend bow.
You automatically get it when you recruit Groudon, from Magma Cavern - Pit. :3
you are able to get groudon later in the game and the flying red and blue dragon, but you have to beat the game
In solar cave you get there after you beat rayquaza
Groudon is located in Magma Cavern. He has a -10 chance of recruiting.
you cant find cranidos in mystery dungeon blue/red its a sinnoh pokemon and rescue team red/blue is based on hoeen which came before sinnoh so no, you cant recruit it but you can recruit it in mystery dungeon sky/time/darkness hope this helped!
No, you can't, because when Pokemon Mystery Dungeon Red came out the Sinnoh Pokemon didn't exist yet.
purity forest
Yes you can
Of course you can!
kill them they will join automatically (!!!not sure!!!)
about 90%
If you're talking about Pokemon Mystery Dungeon Explorers of Time or Pokemon Mystery Dungeon Explorers of Darkness, you can recruit as many Pokemon as you want. If you are talking about Pokemon Mysatery Dungeon Blue Rescue Team or Pokemon Mystery Dungeon Red Rescue Team, you can only recruit a certain number of Pokemon per friend area.