apply-templates in reverse order

Easy!

<xsl:template match="/">
    <xsl:apply-templates select="root/node">
        <xsl:sort select="position()" data-type="number" order="descending"/>
    </xsl:apply-templates>
</xsl:template>

<xsl:template match="node">
    <xsl:value-of select="."/>
</xsl:template>

You can do this, using xsl:sort. It is important to set the data-type="number" because else, the position will be sorted as a string, end therefor, the 10th node would ge considered before the 2nd one.

<xsl:template match="/">
    <xsl:apply-templates select="root/node">
        <xsl:sort 
            select="position()" 
            order="descending" 
            data-type="number"/>
    </xsl:apply-templates>
</xsl:template>
<xsl:template match="node">
    <xsl:value-of select="."/>
</xsl:template>