Rayquaza/Groudon/Kyogre each are level 70 and the only legendaries.
And Latios/Latias
The best Pokemon to catch in emerald is rayquaza. It has great speed and awesome strength. If you teach it the right it might the strongest 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!
Zigzaggoon
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.
Pokemon emerald is based on the hoen pokemon..since it is the hoen region.Look in a site called bulbapedia[best site for pokemon].
No you cannot catch Celebi in Pokemon Emerald.
you cant. You can only catch it in Pokemon emerald, but, you cant catch latias in emerald.