3 Questions: 1.Please could someone give me a good team for defeating..

Your P.S answer:Yes.1:Well,good party you got allready now but raise levels like when all are in lvl 55-60 then it's good.2:-3:No.She only gives herbs and poke snacks.

Get Lugia to level 56 or over then it's easy all the way

1. Yes, you have a fine team. His team is made ENTIRELY of Shadow Pokemon, so the more Shadow Pokemon you use the less powerful his moves are on you. He has the 3 Legendary Birds, all Lv. 50, so you want an Electric Pokemon (Flaafy, Jolteon, etc.) and maybe an Ice Pokemon (Snorunt would be a good choice). He has three other Shadow Pokemon, but they are of little consequence (I'd bring Lapras into this battle to take them on).

2. I don't know anything about ARs.

PS- Yes, you should have kept Lugia as a Shadow Pokemon. But, what's done is done, so you'll just have to make do. I'd go battle the dudes in Dual Square in Pyrite town, to train your Pokemon as well as earn some money.

Hmm.. That means that you're in a spot of trouble. How many Pokemon over Lv. 44 do you have that are still shadow Pokemon? And is Electabuzz still a Shadow Pokemon? Use Shadow Half until they're really weak and then throw balls. If you need money go to the Pyrite Colosseum- you get about 2000 and over and it' easy to beat. Forget your team- you should have kept Lugia as a shadow Pokemon. its high defence and special defence, plus its shadow status, makes it extremely hard to KO while facing greevil and his team of shadows. Try getting another high-defence and sp-defence and high-level shadow pokemon and team it with electabuzz.

I'm sorry, I don't know a thing about Action Replay..

Hope I helped!
Prof. Eevee

Sorry, I can't help you with the Action Replay codes, but I can help you with your little Greevil problem.
And yes, you should have kept Lugia a Shadow Pokemon a little longer, but let's work with what you've got.

1. Do you have the Amulet Coin? If you do this process will go alot faster, if not, it is still possible to do this, it's just alot longer. Go to Mt. Battle and equip the Amulet Coin to one of the Pokemon at the front of your party, then head into the areas and start battling, the Amulet Coin doubles your monitary earnings at the end of a battle, and through this method you can get money to buy Ultra Balls for Snagging his Shadows.
2. Here are Greevil's Pokemon before and after you beat him the first time, their levels and some strategies to beat him (I'm sorry I can't give you their Shadow moves but mine are all purified now and I can't remember all their Shadow moves, sorry, but I can remember that each Bird had one uniqe Shadow move, and I'll try my best to remember them for you):
Before:
Zapdos (Shadow) Lv. 50 Electric/Flying (Shadow Thunder)(I think)
Moltres (Shadow) Lv. 50 Fire/Flying (Shadow Burn)
Articuno (Shadow) Lv. 50 Ice/Flying (Shadow Freeze)
Rhydon (Shadow) Lv. 46 Rock/Ground
Tuaros (Shadow) Lv. 46 Normal
Exeggutor (Shadow) Lv. 46 Grass/Psychic
After:
Swellow Lv. 50 Normal/Flying
Manetric Lv. 50 Electric
Starmie Lv. 50 Water/Psychic
Granbull Lv. 50 Normal
Altaria Lv. 50 Dragon/Flying
Aerodactyl Lv. 50 Rock/Flying
3. (Sorta)
Next, is your Snorlax still a Shadow Pokemon? If so, use that to whittle down the Birds, if not, use that to whittle down the Birds, it won't be the same as using the shadow Lugia to do the job, but it'll be a suitable replacement. Also teach it Protect, which you can find at the Realgam Tower Poke Mart, it's not that expensive, 3,000p. A Snorlax is always hard to faint, what with it's large HP bar and very high Defence ratings, so he should do, and use Protect sparingly, you don't wan't to have it failing you when you most need it. Greevil's other Shadow Pokemon are standard procedure, and you know what to do with them.
4.
Now the strategies I promised.
Before:
Zapdos/ Watch out for that Shadow Thunder I mentioned cause it tends to easily Paralyse your Pokemon and even if you bring a Ground type that still won't work cause remember, it's a Shadow move. As for how to bring him down enough to capture him, I concur with the other guy, use Shadow Half once or twice then get out a Pokemon that knows False Swipe, Pinser or Mawile will do fine, and raise both of them to a fairly high level, say 60, 65. (they will also assist you in snagging up any Pokemon you may have missed from Miror B., and capturing the final Dragonite (Lv. 55 Dragon/Flying) from him as well.) remember, these are Legendarys, so they won't give up without a fight. But just stick to this strategy and you should do fine, but please note: DO NOT USE THE SNORLAX WHILE ATTEMPTING THIS SHADOW HALF STRATEGY! Unless you use Protect on Snorlax first, in which case it's okay, remember the whole point of putting Snorlax into the battle is to give your guys time to whittle down the Birds health so that you can snag'em.
Moltres/Same strategy as before, except watch out for Shadow Burn, this one has a nasty tendency of Burning your Pokemon.
Articuno/Same afformentioned strategies and don't worry too much about Shadow Freeze, Pokemon don't get Frozen very often, nevertheless bring alot of Full Heals in addition to your Ultra Balls to the battle, and some Ice Heals if you want to.
As for the rest of his Pokemon, they're standard procedure, just keep in mind that the Rhydon is a Rock/Ground Type, so False Swipe won't be very effective against him.
After:
Swellow/Manetric/ He usually throws them out onto the field together, and Manetric has the ability Lightningrod, which will protect Swellow from your Electric attacks, so what I suggest is that you take out Manetric with Earthquake, then go after Swellow with an Ice type attack, perferably Ice Punch or Ice Beam, so as not to activate Manetric's Lightningrod in case Earthquake doesn't go first.
Starmie/ Well Starmie's a Water/Psychic type, so you can use either Dark or Electric, I perfer Electric myself, but it's really up to you which one to use.
Granbull/ He's not particularly strong, so you shouldn't have much trouble with him, and he's a Normal type, so bring Fighting moves to the battle, my suggestion, train up an Electabuzz, let it learn Cross Chop and use it to KO Granbull, but watch out because Granbull knows Earthquake.
Altaria/ Altaria is a Dragon/Flying type so just use the Ice moves you used to KO Swellow before and you're golden.
Aerodactyl/ Rock/Flying, nevermind the Rock type, Zap it with Electrical moves and you should be just fine.
5.
As for your new Party, and array of moves, here's what I think you should go with:
Old Team:
Shiftry : Level 47
Lugia (Purified): Level 50
Dusclops: Level 53
Marowak: Level 44
Ninetales: Level 49
Salamence: Level 51
New Team to take on Greevil with the first time:
Snorlax (if not a Shadow Pokemon) Lv. 60 or higher
Rest
Snore or Sleep Talk
Protect
Earthquake
Pinser Lv. 60-65 or higher or Mawile Lv. 60-65 or higher
Guillontine Metal Claw
Submission Sing
Vicegrip Vicegrip
False Swipe False Swipe
Electabuzz Lv. 60 or higher
Thunder
Ice Punch
Cross Chop
Thunderbolt
Lugia Lv. 60 or higher
Psychic
Hydro Pump
Earthquake
Recover (see the Move Tutor on Mt. Battle)
Any Shadow Pokemon with Shadow Half
Salamence Lv. 60 or higher
Dragon Claw
Dragonbreath (see the Move Tutor on Mt. Battle)
Aerial Ace
Fly (see the Move Tutor on Mt. Battle)
________________________________________________________
After:
Same team, but take out the Pinsir/Mawile and the Shadow Pokemon and put in Lapras Lv. 60 or higher
Ice Beam
Blizzard
Sing
Surf
__________________
And
Gardevoir Lv. 60or higher
Psychic
Shock Wave
Hypnosis
Dream Eater

Well these are my answers to your question/request, I hope I helped you to finish your game.
Best hopes, CrystalTitan1