Where is mewtwo and can you get mew?

Mewtwo:
Once you go back to Mt. Faraway and recruit Ho-oh on your team an event
will be started once you arrive back at your Rescue Team base. This was
my personal favorite event as it involves Mewtwo, and just how it was
portrayed. After it's over head to the town square where the Charizard
and Blastoise you saw will come up to you injured letting you know about
Western Cave. This will unlock the cave for exploration, to head here
all you need is the HM Surf or a water Pokemon who knows it.

This cave is 99 Floors and the first place where I really felt handicapped
Belly-wise. I should have put a Stamina Band on my leader (who knows
Trap Seer or I'd wear No-Stick Cap). What I did to counter the hunger
issues, was pickup every berry/seed I saw, and ate them (each gives 5
Belly back), except for seeds that confuse you. Also I found a Kecleon
shop 20-30 floors up, that had 4 Gummies all cheap which I could easily
afford (Gummies give alot of belly and I was forced to eat a few of em).
The Gummies along with the Berrys/Seeds and the 2 Huge Apples I brought
managed to easily get me to Floor 98, in fact my Belly was full when I
found Floor 99's stairs so I sat near the stairs utilizing A+B and let
some Charizards and Blastoises come to me for some nice exp.

This dungeon is my favorite place in the game to level, some prefer the
1-room monster houses in Silver Trench, but just one clear here I
accumulated approximately 10 levels (went from mid-60s to mid-70s).
There is nowhere in the game that can match that experience as far as
I know.

Mewtwo is waiting for you at the end, but if your stats are buffed and
you managed to make it through all 98 previous floors of those difficult
Pokemon, he should be a pushover for you.

Note: Mewtwo's recruit % is 99.9, but you cannot recruit him until the
2nd time you encounter him. Also his body size is 1 which makes
him that much easier to recruit since you can bring 3 Pokemon as
long as their body sizes don't hit the maximum total of 6.

For Recruiting purposes: Mewtwo is lvl 40 when recruited.

Mew: Buried Relic:
After you have cleared the Stormy Sea, you should receive a mail in you
mailbox about the Buried Relic. All you have to do after that is head
to the Town Square and talk to Shiftry and Lombre to unlock this massive
dungeon.

Mew: is lv. 40 when recruited!
His Rcruitment rate is 1.0, which MEANS you NEED the Friend Bow, and need to be lv. 90+! And, YOU need to kill him(NOT your other team members!!). AND, you NEED to be RIGHT IN FRONT OF HER( 1-tile away!)!!! And, you'll need to have the Music Box in your toolbox, and DON'T make ANYONE Hold it, and DON'T Use it!! He is between floors 36 - 98. He appears RANDOMLY,and transforms into ANY Pokemon so keep an eye out!and, if you see a pokemonusing an UNUSUAL move, Hold the Friend Bow, and got to it RIGHT AWAY!!