jdown | Transform a directory of markdown files to JSON | Static Site Generator library

I would just put all game code on frame 1.

Also make a new MovieClip on frame 1 called levelsMC that is a container all the level frames (use "cut frames" from stage timeline & paste them inside the levels MC timeline),

Now your code can just say for level 2 = levelsMC.gotoAndStop(2); or for level 3 levelsMC.gotoAndStop(3);...

Because code and levelsMC are both on frame 1, you don't have to transfer (re-copy) any code.

Your working logic would be :

I have the first frame with one button ( levelButton ),

• I have a variable nextLevel (integer) that has frame number. I update as nextLevel = 2;
• The first button tells levelsMC go to first level (using levelsMC.gotoAndStop(2);) or can use levelsMC.gotoAndStop(nextLevel);
• the second button go to second level (using levelsMC.gotoAndStop(3);)

• and goes on until the final level in frame 21 (levelsMC.gotoAndStop(21);).

• I write all of my code in frame 1 and to show from level 1 onwards I say :
  startScreenMC.visible = false; and levelsMC.visible = true;

• When the player complete the stage I update nextLevel number (integer) as +1 and i'm ready to click to levelButton, where click/tap function simply tells levelsMC to got frame x (where x is nextLevel amount) like this :
  levelsMC.gotoAndStop( nextLevel );

PS: Look into AS3 linkage tutorials. Makes it easier to create an MC of coin or charatcer and just addChild that to levelsMC when needed. Then code access it via path like levelsMC.coin = visible = false; etc.