You can use the gifAnimation library. It allows to access the current image, or even the whole array of images, and you can manipulate them like any other regular Processing images.

Okay, thank you, I understand... but... here my try...
Error: The constructor Gif(a_game_2.explosion_01,String) is undefined.
Why... :-(

sketch:
import gifAnimation.*;
explosion_01 boom = new explosion_01();

tab:
public class explosion_01 {

  import gifAnimation.*;

  Gif LoopingGif;

  explosion_01 () {
    registerDraw(this);
  }

  void setup()
  {
    LoopingGif = new Gif(this, "graphics/explosion_01.gif");
    LoopingGif.loop();
  }

  void draw()
  {
    image(loopingGif, 10, height / 2 - loopingGif.height / 2);
  }
}

I think that might have something to do with the way you're using tab and the use of the this keyword.
The Gif constructor should have two arguments : the sketch PApplet object and the name of the gif file you want to load.
Calling this within a tab would not return the sketch PApplet object. That's why you got the error.
This as been adressed in several thread.

You can use the sketchname.this (like a_game_2.this) to get it works.
However you should have a setup() and draw() methods in your sketch window too

Okay, now it works! But...

Try 1) I could load the AniGif on sketch - but if i duplicate it, all animations play the same way.

Try 2) I could load the AniGif on class- the animations are now different, evry load stops the window for a little moment.

With the old way...

PImage[] gifImages = new PImage[gifFrames];
PImage background_pic;

  for(int i=0; i<gifFrames; i++) {
    String imageName = "graphics/explosion_01/explosion_" + i + ".gif";
    gifImages[i] = loadImage(imageName);
  }

(...)

...everything is working, but I have to extract all aniGif... hmmm...

Show full code, we can't guess how you messed your code, there are so many ways to do that...