XML with several levels to XML with one level using XSLT

I am new to XSL and I have two questions regarding several child elements.

I have the following structure in my XML document:

<root>
  <levelOne>
  <entry1>Test1</entry1>
  <entry2>Test2</entry2>
    <levelTwo>
      <entry3>Test3</entry3>
      <entry4>Test4</entry4>
      <levelThree>
        <entry5>Test5</entry5>
        <entry6>Test6</entry6>
      </levelThree>
    </levelTwo>
  </levelOne>
  <levelOne>
  <entry1>Test1</entry1>
  <entry2>Test2</entry2>
    <levelTwo>
      <entry3>Test3</entry3>
      <entry4>Test4</entry4>
      <levelThree>
        <entry5>Test5</entry5>
        <entry6>Test6</entry6>
      </levelThree>
    </levelTwo>
  </levelOne>
  <!-- etc. -->
</root>

My XSL looks like this:

<xsl:stylesheet version='1.0' xmlns:xsl='http://ift.tt/tCZ8VR'>
<xsl:output method="xml" indent="yes"/>
<xsl:template match="root">
<resultlistEntries>
    <xsl:for-each select="levelOne">
        <entry1><xsl:value-of select="entry1"/></entry1>
        <entry2><xsl:value-of select="entry2"/></entry2>
        <!-- address child elements? -->
    </xsl:for-each>
</resultlistEntries>
</xsl:template>
</xsl:stylesheet>

I want entry 3, 4, 5, 6 etc. to be one the same level in my output XML document.

1. How is it possible to address a child element of a child element (3rd, 4th, etc. level)?


2. How is it possible to have all those child elements on one level (in resultlistEntries, in my example)?