I have found some solutions (e.g http://stackoverflow.com/questions/16697366/java-applet-using-javafx) how to embed JavaFX in Swing JApplet but any of these solution is showing how to properly make start() method for the reason of reloading applet.
For sure start() is called after init() a before paint() and every time when applet is reloaded.
I have tried some approaches by myself but anyone has properly worked.