i go to cape brink with a feraligatr, thyplosion, meganium, blastoise and venasaur
then i talk with the girl that teach Frenzy Plant, Blast Burn or Hydro Cannon

and says this:

"I prefected the ultimate move of its type...
But will no one take it for future use?
...Hm? Hmmm!
Y-you...
Th-that VENASAUR
...No...
I was just mistaken"

i have hydro cannon for blastoise but it's supposed to teach to a Blastoise, Meganium, Thyplosion, Feraligatr and Venasaur

Is your Venusaur at maximum happiness? If not, that could be the problem.
And why exactly do you want the ultimate move, anyway? It's not very good, compared to something like Surf, Flamethrower, or... okay, Frenzy Plant is good I guess, since Solarbeam also takes two moves to fire.

coz they look great in battle

Looks aren't everything, my friend.

Check the psydex for the moves exact power

Does anyone know if you can breed the Ultimate Moves down (IOW, as egg moves)?
Also, can they be taught twice (ex. Blast burn to 2 different Charizards, one your starter, and another you got from a trade?) I think not because she no longer sais "I perfected the ultimate move of its type..."

Actually, I took my starter Venusaur to her and it learned Frenzy Plant, and then I took a traded Charizard to her, and it was able to learn Blast Burn. It worked with a traded Blastoise too. And I don't think Meganium, Feraligatr and Typhlosion are able to learn these moves.

The venasuar problem happened to me too,i was like wtf!?! so i thought if i raised it a lvl it wud work and it did

But i chose bulbasaur as a starter and I traded charmander and squirtle from another game. When I finally reached Cape Brink, Charizard learned Blast burn, Blastoise Hydro cannon, but Venusaur, [u][b]MY STARTER[/b][/u], did not learn Frenzy plant. How's this ?

like theKid said, could it have something to do with level? What level was your Charizard, Blastoise, and Venusaur?

At what level did u raise Your venasaur up to anyway...the Kid ?( Because im getting the same problems with my Lv50 Venasaur ,I talk to the lady but at the end of her sentence it says...No...It was Mistaken...)

I believe it's happiness that is the key. Of course, I don't really go to Cape Brink 'cause I've never been good with Hyper Beam-like moves.

I also tried before with a Venusaur (not mine) which has pretty high happiness, but it doesn't work. Why not??!

EDIT: I fix your spelling! -papersun

Did it have max happiness?

im not shore ever my chary is lv 61 i no it but i cnt be lv caus at lv61 be 4 i bet elet4 it said "it cnt be".ps or im totaly worng

Yes, happiness is the key. At least, on D/P.
I'll check it out later on LG, and come back, hopefully, with an answer.

my blastoise learend i at lv 50 but it was at max happiness so I dont know whats wrong

Lemme clear this all up:

The level of your Pokemon does not matter.
It does not need to be your original starter.
The Pokemon's happiness must be at max.
She can only teach each move ONCE, and only ONCE.
Only Venusaur, Charizard, or Blastoise can learn one of those moves in FRLG.
And the moves can't be breeded, or anything.

I know this because...well, experience, because I've done it. - DNA

It was probaly around 44 and I took it and she didnt teach it so I went out side and battle maybe two meowth and it went back and by this time it was at 45 then she taught Frenzy Plant

But like SorcererDNA said its happiness i guess

my venasaur is at level 77 and i still cant learn it, wtf

well, if you traded it, or left it in the PC for a while, its happiness may not be max.

EDIT: nvm about leaving it in the PC...but if it fainted in battle, that would reduce happiness.

TheKid: Just call me DNA. Seriously. I don't like it when people tack the 'Sorcerer' on.
Sion9: PC doesn't affect happiness at all.
For anyone else who wants to get their Poke's happiness up, read the Happiness Guide if you have any questions or doubts.
- DNA

actually
as long as you own[that you are the original trainer]
of any1 of the LGFR starters, if they become their last evolution they can learn the "ultimate move'
as long as they love you
and that it can ACTUALLY BE BREEDED DOWN

eg;
a MALE charizard has Blast Burn
when you breed it say.. with ditto...
it can pass the Blast Burn move to the baby charmander