You can't. Yoshi is not a pokemon.
Yes, You can catch Groudon in Pokemon Emerald.
You can't catch one in Pokemon Emerald.
No you cannot catch Entei in Pokemon Emerald.
You can't catch a Bellsprot in Pokemon Emerald. You trade it from Pokemon Leafgreen!
There are many Pokemon you catch that are similar in sapphire and emerald but there are many Pokemon emerald can only get and not sapphire.
Cressilia is a 4th generation Pokemon so you can't catch it in Pokemon Emerald.
You can't catch or obtain other trainers Pokemon in emerald.
you cant. You can only catch it in Pokemon emerald, but, you cant catch latias in emerald.
No you cannot catch Celebi in Pokemon Emerald.
You can onl catch LUNATONE in SAPPHIRE but you can catch solrock in emerald
You cannot catch Entie in Pokemon Emerald. You can catch Entie in FireRed, LeafGreen, HeartGold, and SoulSilver. You can trade Entie to Emerald from FireRed and LeafGreen.
You can trade it from Pokemon Emerald. In Pokemon Emerald, when you find Rayquaza, there is a small chance that it is shiny when you find it. Save the game right before you fight him and keep trying until it turns black. Then catch it and trade it to Pokemon Diamond.