XSLT piping, Staging

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="2.0">

    <xsl:template match="/">
        <xsl:variable name="fullxml">
                <xsl:apply-templates/>
        </xsl:variable>
        
        <xsl:apply-templates select="$fullxml" mode="s2"/>
    </xsl:template>

<xsl:template match="a">
    <b>
        <xsl:apply-templates/>
    </b>        
</xsl:template>

    
    <xsl:template match="b" mode="s2">
        <c>
            <xsl:apply-templates mode="s2"/>
        </c>
    </xsl:template>
     
</xsl:stylesheet>

Input XML
<?xml version="1.0" encoding="UTF-8"?>
<element-group>
    <a>Saai</a>
    <a>121212</a>
    <a>23232</a>
    <a>vfvfvfv</a>
    <a>frrfrf</a>
    <a>bgbgbg</a>
    <a>bgbgbgbg</a>
</element-group>




Stage one Output
<?xml version="1.0" encoding="UTF-8"?>
<b>Saai</b>
<b>121212</b>
<b>23232</b>
<b>vfvfvfv</b>
<b>frrfrf</b>
<b>bgbgbg</b>
<b>bgbgbgbg</b>


Stage Two Output
<?xml version="1.0" encoding="UTF-8"?>
<c>Saai</c>
<c>121212</c>
<c>23232</c>
<c>vfvfvfv</c>
<c>frrfrf</c>
<c>bgbgbg</c>
<c>bgbgbgbg</c>