It can only be obtained in amity square in hearthome city (or lady in pastoria), it's very rare to find though.
It is possible to obtain a Custap berry in Pokemon Pearl. To get it you have to trade from Ruby, Sapphire or Emerald version.
You want to use a berry that has a circle around bitter on its tag, here are some berries you can use: Durin, Rabuta, Rawst.
No such thing.
The berry isn't found in the game. You get it in events only. Sometime in the end of Feb. '11, there will be an event at gamestop stores where you can get a Celebi who is carrying this berry.
you spelled pearl wrong
A Pokemon that can learn moves for the contest you want to enter in, using pokeblocks made from berries like spelon berry or durin berry or ganlon berry or belue berry or pamtre berry or watmel berry or salac berry or leichi berry or petaya berry will give you better levels and less feels expeccially if you blend with 4 people.
Occa berry.
east of hearthome city
There is only one berry house throughout the whole of Pokemon diamond/pearl but there is a flower shop where you can get free berries in floaroma town.
You can do that by keep on battling with that Pokemon, or using a specific type of berry.
Amity Square(walk 200 steps and your Pokemon might be holding the berry)
all of 'em