I've built an example for you in SQL Server using your data:
DECLARE @StackExample TABLE (
Id UNIQUEIDENTIFIER NOT NULL PRIMARY KEY DEFAULT(NEWID())
,XmlColumn XML
)
INSERT INTO @StackExample(XmlColumn) VALUES('<info>
<StInfo>
<name>William</name>
<address>India</address>
</StInfo>
</info>')
UPDATE T
SET XmlColumn = XmlColumn.query('<info>
<Student>
{info/StInfo/*}
</Student>
</info>')
FROM @StackExample t
SELECT * FROM @StackExample
I hope this can help