In the cave with all the dots that are supposed to be words, WH..

If the cave your talking about is the Sealed Chamber, then yes. It's called
Braille. When you first enter the Sealed Chamber, you'll see 10 rocks. On
Each of those rocks is writing. It shows the whole alphabet in order. At the end
Of the room you'll see more Braille. To get into the next room, stand in the middle
Of the writing, then use dig(it won't get you out of the Sealed Chamber, if you stand in the right place). In the last room, you'll see 7 more rocks. The six rocks in the front are basically nonsence. Last but not least, the rock in the back. That
One says something(forgot what it said), but you'll need a Wailord and a Relicanth to get the Regis.( Regirock, Regice, and Registeel) For more info about Braille, look in the back of the Emerald Official Players Guide.

They are the ABC's in one room but in another it says something about the Regi's, That place is the main onjective of getting the Regi's.

I have solved all that written in Braille. It took me a lot of time and battery.

The underwater panel says, [Go Up Here.]

In the first room,there are just alphabets from top left to bottom right leaving only the two in right.
They are : 1. A comma 2. A full stop
The top panel says, [Dig Here.]

In the second room,
Top left panel: [In This Cave, We Have Lived.]
Top right panel: [We Owe All To The Pokemon.]
Centre left panel: [But, We Sealed The Pokemon Away.]
Centre right panel: [We Feared It.]
Bottom left panel: [Those Have Courage, Those Have Hope.]
Bottom right panel: [Open A Door. An Eternal Pokemon Waits.]
And, the top panel says, [First Comes Wailord.Last Comes Relicanth.]


Now, I think you have got all your answers.