Ok, I've looked in lots of places without finding any answers.
I live in Europe, so I'm forced to play Chrono Cross using an emulator and a downloaded rom.
That means I don't have a manual.

What I don't understand is the "lvl up system".

When do your party "reach a new growth level"?
And when do single stats increase? Like only "hp+2" or "str+1".

And when you "reach a new growth level" the "X/X" increases with one.
Like if it says 9/9 and I "reach a new growth level" it changes to 10/10.
These number also appear on the top of the battle screen if you fill
the "elemental ring" with one color.
What does this mean?

I appreciate any help I get.