Cheats for Pokemon: Sapphire (GBA)
Uncatchable pokemon list
203 - Bulbasaur
204 - Ivysaur
205 - Venusaur
206 - Charmander
207 - Charmeleon
208 - Charizard
209 - Squirtle
210 - Wartortle
211 - Blastoise
212 - Caterpie
213 - Metapod
214 - Butterfree
215 - Weedle
216 - Kakuna
217 - Beedrill
218 - Pidgey
219 - Pidgeotto
220 - Pidgeot
221 - Rattata
222 - Raticate
223 - Spearow
224 - Fearow
225 - Ekans
226 - Arbok
227 - Nidoran [Female]
228 - Nidorina
229 - Nidoqueen
230 - Nidoran [Male]
231 - Nidorino
232 - Nidoking
233 - Clefairy
234 - Clefable
235 - Paras
236 - Parasect
237 - Venonat
238 - Venomoth
239 - Diglett
240 - Dugtrio
241 - Meowth
242 - Persian
243 - Mankey
244 - Primeape
245 - Growlithe
246 - Arcanine
247 - Poliwag
248 - Poliwhirl
249 - Poliwrath
250 - Bellsprout
251 - Weepinbell
252 - Victreebel
253 - Ponyta
254 - Rapidash
255 - Slowpoke
256 - Slowbro
257 - Farfetch'd
258 - Seel
259 - Dewgong
260 - Shellder
261 - Cloyster
262 - Gastly
263 - Haunter
264 - Gengar
265 - Onix
266 - Drowzee
267 - Hypno
268 - Krabby
269 - Kingler
270 - Exeggcute
271 - Exeggutor
272 - Cubone
273 - Marowak
274 - Hitmonlee
275 - Hitmonchan
276 - Lickitung
277 - Chansey
278 - Tangela
279 - Kangaskhan
280 - Mr - Mime
281 - Scyther
282 - Jynx
283 - Electabuzz
284 - Magmar
285 - Tauros
286 - Lapras
287 - Ditto
288 - Eevee
289 - Vaporeon
290 - Jolteon
291 - Flareon
292 - Porygon
293 - Omanyte
294 - Omastar
295 - Kabuto
296 - Kabutops
297 - Aerodactyl
298 - Snorlax
299 - Articuno
300 - Zapdos
301 - Moltres
302 - Dratini
303 - Dragonair
304 - Dragonite
305 - Mewtwo
306 - Mew
307 - Chikorita
308 - Bayleef
309 - Meganium
310 - Cyndaquil
311 - Quilava
312 - Typhlosion
313 - Totodile
314 - Croconaw
315 - Feraligatr
316 - Sentret
317 - Furret
318 - Hoothoot
319 - Noctowl
320 - Ledyba
321 - Ledian
322 - Spinarak
323 - Ariados
324 - Cleffa
325 - Togepi
326 - Togetic
327 - Mareep
328 - Flaaffy
329 - Ampharos
330 - Sudowoodo
331 - Politoed
332 - Hoppip
333 - Skiploom
334 - Jumpluff
335 - Aipom
336 - Sunkern
337 - Sunflora
338 - Yanma
339 - Wooper
340 - Quagsire
341 - Espeon
342 - Umbreon
343 - Murkrow
344 - Slowking
345 - Misdreavus
346 - Unown
347 - Pineco
348 - Forretress
349 - Dunsparce
350 - Gligar
351 - Steelix
352 - Snubbull
353 - Granbull
354 - Qwilfish
355 - Scizor
356 - Shuckle
357 - Sneasel
358 - Teddiursa
359 - Ursaring
360 - Swinub
361 - Piloswine
362 - Remoraid
363 - Octillery
364 - Delibird
365 - Mantine
366 - Houndour
367 - Houndoom
368 - Porygon2
369 - Stantler
370 - Smeargle
371 - Tyrogue
372 - Hitmontop
373 - Smoochum
374 - Elekid
375 - Magby
376 - Miltank
377 - Blissey
378 - Raikou
379 - Entei
380 - Suicune
Catch Regice, Registeel and Regirock
First you have to have some Pokemon that know HM03 Surf, HM08 Dive and TMDig. Fly to Paciflog town. Go in the Pokemon Center and withdraw Wailord (evolution of waimer) and Relicanth (If you don't have these Pokemon yet catch a waimer with your super rod in the water near Mossdeap city.)
They are near Lv.35 so you have to train it to Lv.40 for it to evolve. Catch Relicanth underwater to the left of Mossdeap City. He is rare so have patience. Surf left and always stay on the bottom currents.
After you get to the 3rd or 4th square of land, you'll see the deep water. Dive in. Walk all the way to the top. Use Dig. Go through the door and go all the way to the top and read the words. Then press A again and all of the 3 doors (for the 3 regi's) will open. You probably already passed them before.
Get Mystery Events option
To get Mystery Events, go to Petalburg City pokemon center and talk to the guy that asks about your profile. Enter this:
Mystery Event Is Exciting
He will say that you are now a Mystery Events Club member, which unlocks Mystery Events in the New Game/Continue menu.