Hi Amit,
You need to add the v21 namespace to your XSL. It will be:
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:v2="test.com" xmlns:v21="http://www.test.com/v21" exclude-result-prefixes="v2 v21">
<xsl:output omit-xml-declaration="yes" indent="yes"/>
<xsl:template match="/soapenv:Envelope">
<soapenv:Envelope>
<soapenv:Header>
<soapenv:Body>
<Header>
<xsl:apply-templates select="soapenv:Header/v2:XHeader/node()"/>
</Header>
<Body>
<xsl:apply-templates select="./soapenv:Body/v21:Info/node()"/>
</Body>
</soapenv:Body>
</soapenv:Header>
</soapenv:Envelope>
</xsl:template>
<xsl:template match="soapenv:Header/v2:XHeader/node()">
<xsl:element name="{local-name()}">
<xsl:apply-templates select="@* | node()"/>
</xsl:element>
</xsl:template>
<xsl:template match="./soapenv:Body/v21:Info/node()">
<xsl:element name="{local-name()}">
<xsl:apply-templates select="@* | node()"/>
</xsl:element>
</xsl:template>
</xsl:stylesheet>
Regards.