Semantic HTML4 Mobile Accessibility Support

HTML Element or Attribute VoiceOver on iOS 7.1.2 VoiceOver iOS 8.3 TalkBack 3.5.1 with Chrome 37 on Android 4.4.4 TalkBack 3.5.1 with Firefox 32 on Android 4.4.4
fieldset <legend> Not Supported Not Supported Not Supported Supported
<th> Supported (bugs) Supported (bugs)   Supported
<caption> Supported Supported    
<th> scope Not Supported Not Supported Not Supported Supported
<td> headers Not Supported Not Supported Not Supported Supported (only if pointing id reference to <th> elements it seems?)
<img alt> Supported Supported Supported Supported
<img> longdesc Not Supported Not Supported Not Supported Not Supported
title attribute Supported (focusable elements only) or IMG Supported (focusable elements only) or IMG Supported (but aria-label cancels out title) Supported (reads both title and aria-label)
lang attribute Supported Supported Not Supported Not Supported
<abbr title> Not Supported Not Supported   Supported