XSLT: Convert Name/Value pair and transform an XML - xslt-1.0

Question

I need to convert a name value pair into XML. I'm able to generate an XML, but the element name should be grouped and it should not be duplicated. Please see below. The FieldValue element contains 2 OrderItem values in the Detail node. If the FieldValue with OrderItem repeats, then the result should be grouped into one OrderItem node. Please help.
Source XML:
<SC>
<Header>
<Record>
<FieldName>Schema</FieldName>
<FieldValue>OrderHeader</FieldValue>
</Record>
<Record>
<FieldName>Order</FieldName>
<FieldValue>1234</FieldValue>
</Record>
</Header>
<Detail>
<Record>
<FieldName>Schema</FieldName>
<FieldValue>OrderItem</FieldValue>
</Record>
<Record>
<FieldName>Item</FieldName>
<FieldValue>1</FieldValue>
</Record>
<Record>
<FieldName>Qty</FieldName>
<FieldValue>10</FieldValue>
</Record>
</Detail>
<Detail>
<Record>
<FieldName>Schema</FieldName>
<FieldValue>OrderItem</FieldValue>
</Record>
<Record>
<FieldName>Item</FieldName>
<FieldValue>2</FieldValue>
</Record>
<Record>
<FieldName>Qty</FieldName>
<FieldValue>20</FieldValue>
</Record>
</Detail>
</SC>
Target XML:
<Order>
<OrderItem>
<Item>
<Item>1</Item>
<Qty>10</Qty>
</Item>
<Item>
<Item>2</Item>
<Qty>20</Qty>
</Item>
</OrderItem>
</Order>
XSLT:
<xsl:template match="#*|node()">
<Order>
<xsl:for-each select="Detail">
<Item>
<xsl:apply-templates select="Record[position()>1]"/>
</Item>
</xsl:for-each>
</Order>
</xsl:template>
<xsl:template match="Record">
<xsl:element name="{FieldName}">
<xsl:value-of select="FieldValue"/>
</xsl:element>
</xsl:template>

Answer 1

The grouping can be done as follows:
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
exclude-result-prefixes="xs"
version="2.0">
<xsl:output indent="yes"/>
<xsl:template match="SC">
<Order>
<xsl:for-each-group select="Detail" group-by="Record[1]/FieldValue">
<xsl:element name="{current-grouping-key()}">
<xsl:apply-templates select="current-group()"/>
</xsl:element>
</xsl:for-each-group>
</Order>
</xsl:template>
<xsl:template match="Detail">
<Item>
<xsl:apply-templates select="Record[position() gt 1]"/>
</Item>
</xsl:template>
<xsl:template match="Record">
<xsl:element name="{FieldName}">
<xsl:value-of select="FieldValue"/>
</xsl:element>
</xsl:template>
</xsl:stylesheet>

Answer 2

It appears that you are trying to define two XSLT templates, when one should be sufficient. You want to match on the root and then that you want to iterate over each SC/Detail.
Then, you want to take the FieldValue of the sibling of the FieldName node that is 'Item' (for item value) and 'Qty' (for quantity value), but only those listed under 'Record'.
Note: You have specified a doubly-nested <Item> in your transformed output and this solution reflects that requirement.
This XSLT should do what you are requesting:
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
<xsl:template match="/">
<xsl:for-each select="SC/Detail">
<Order>
<OrderItem>
<Item>
<Item>
<xsl:value-of select="Record[FieldName[text()='Item']]/FieldValue" />
</Item>
<Qty>
<xsl:value-of select="Record[FieldName[text()='Qty']]/FieldValue" />
</Qty>
</Item>
</OrderItem>
</Order>
</xsl:for-each>
</xsl:template>
</xsl:stylesheet>