Question

I need to render an expandable list which initially displays around 6-8 items list but on clicking 'Show all' it should show the entire items list.

Answer 1

No PrimeFaces component comes to mind, but how about just this?

<h:form>
    <ul>
        <ui:repeat value="#{bean.list}" var="item" varStatus="loop">
            <ui:fragment rendered="#{loop.index lt 6 or bean.showAll}">
                <li>#{item}</li>
            </ui:fragment>
        </ui:repeat>
    </ul>
    <h:commandButton value="Show all" action="#{bean.setShowAll(true)}" rendered="#{!bean.showAll}">
        <f:ajax render="@form" />
    </h:commandButton>
</h:form>

with

@ManagedBean
@ViewScoped
public class Bean implements Serializable {

    private List<String> list = Arrays.asList("one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten");
    private boolean showAll;

    public List<String> getList() {
        return list;
    }

    public boolean isShowAll() {
        return showAll;
    }

    public void setShowAll(boolean showAll) {
        this.showAll = showAll;
    }

}

You could wrap it if necessary in a composite.