How many form elements do you have? Keep in mind that a a4j:commandButton cannot submit a different form. Also, popups by default are rendered outside of the form, either embed a form in them, or use domElementAttachment to get the popup to participate in another form.
Thanks for the reply.
i can able to assign the values to parent form once i clk on the h:commandlink from rich:popuppanel successfully and i am using h:commnadButton in the second tab to call Save method of my bean class but its not calling and directly its moving to init()(postconstruct) method of my bean class. I am not understanding where i am doing wrong.
Looking at your secondpage.xhtml, I don't see any form tags. How are you using that page?