Beaten game and trying to figure stuff out

So if you want the optional mission I can help you with that just follow this tips:

If you've read all LOVELESS inscriptions, you can take an optional path.

At Oblivion Lake, there are 5 points where the Lifestream is very strong. If
You press X at any of those 5 points, you'll face a tough creature which looks
Alot like the monsters in the pods at the Nibelheim Reactor. If you beat these
5 Genesis clones, a bridge will connect to a new area at the north. Dodge their
Attacks and attack with Costly Punch to have a fairly easy time. Save and head
Over the bridge to the Cage of Binding.

You must fight creatures in order to proceed with the game. The creatures drop
Keys which are used to unlock doors. The following creatures drop the keys:

Goddess Base Key: Nightmare (purple Dorky Face; Looks like a flying pumpkin)
Goddess Sacral Key: Nightmare (purple Dorky Face; Looks like a flying pumpkin)
Goddess Solar Key: Mover (three bouncing orbs)
Goddess Heart Key: Mover (three bouncing orbs)
Goddess Throat Key: Death Machine (looks like a sweeper)
Goddess Third Eye Key: Evil Eye (looks like one-eye)
Goddess Crown Key: Grosspanzer (STRONG, 78600 HP, looks like General Tank)
Goddess Wing Key: Behemoth King

In this area you'll come across quite a few cells with treasure. Turn the valve
At cell #1 to find a chest with a [�RIVER CHOCOBO ARMLET]. Fight the
Nightmare creatures in this room to get a Goddess' Base Key. Use it to open the
Door. In The next hall, cell #4 holds an [�ELIXIR]. Head downstairs, open up
Cell #5 and grab the [�GRAVITGA (M)]. Open up the door with the Goddess' Sacral
Key.

In this area, the hole in cell #9 leads to cell #8, allowing you to grab a
[�DISPEL BLADE]. Go through the door, and through the next one also that comes
In sight. Here, unlock cell #12 which leads back to a cell in the previous
Area. Also open up cell #13 to find a [�PHOENIX DOWN]. The door here is
Locked, so go back to the hall and continue. Open up cell #16 which leads to
Cell #15 to find the [�LABORATORY KEY], which opens the previously locked door.
Head back and open it up.. That is, if you want to, because you can only read
Some notes here, and fight the 4 strong materia that are similar to the ones
Sephiroth summoned in battle.

Proceed through the hall and go inside cell #17 for a [�GRIS-GRIS BAG] and a
Save Point. Proceed through the gate, and head east. To the right, open up
Cell #19, and ignore the hole, which only leads the beginning of Howling Fang
Where you'll end up later anyway. Head north from cell #19, and open up cell
#20 here for a [�MAG Up+ (M)]. Cell #23 holds a [�SILVER ARMLET]; You can
Ignore cell #22.

Head west to end up in the main hall again. Walk up the stairs to the west and
Go through cell #27 (which links to cell #18) to find a [�HP Up++ (M)] and a
[�ATK Up+ (M)]. Head back to the main hall and go down the stairs on the
Northwest, near the gate. You'll find another gate here, so open it up and
Find a chest with the [�IRON BARS KEY] in cell #31. Backtrack (and fight a
Very strong enemy called Gross Panzer on your way back) and open up the gate in
The main hall.

Now it's just a matter of walking down the stairs and going through cell #32 at
The end, which links with cell #36, right before Behemoth King. Save your game,
Then open the cell door to fight Behemoth King, which has 138780 HP. It drops
The last Goddess Key, so head over to the last gate and open it up to find..
Nothing! I'm sorry to dissapoint you, but that was the entire final area. The
Reward you've gotten were the items that you gotten on your way (which
Admittedly held some nice items). Now you're at the Portal of Severance
Again. Save your game.

Hope it helps! Good luck!

Just want to say sumfin to the above comment

An easy way, the easiest way to win against those 5 copy things is to use blast wave or any move tht has the word blast in it

I can`t find the last materia to open this big door. Can someone help me?