What the heck are SVG styles?
If you're talking about regular old CSS styles, then I can assure you that they work in ADE (both external and inline style sheets, as well as inline styles). I can't begin to vouch for iBooks, but I know I've heard other people mention that one works better than the other, I just don't remember which.
I'm not sure what your first example is meant to be, but it's not the correct syntax for linking to an external CSS style sheet. This
<link href="svg-stylesheet.css" rel="stylesheet" type="text/css" />
and it should be placed in the HEAD section of the html document (it also assumes that your external stylesheet is in the same folder as your (x)html document. Adjust the href accordingly if not)
It's hard to tell what may be wrong with your second example without seeing what HTML you are trying to style
with it. But for starters... if you're going to go the CDATA route, then make sure you take it all the way (and it should be placed in the head section):
<style type="text/css" >
Your third example shouldn't work at all in any ePub reading system. Inline styles should take the form of:
<p style="font-family:Baskerville;font-size:20px">Sample text</p>
Which also assumes that the Baskerville font is available to the reading system. Otherwise, you'll need to switch to a style sheet and use @font-face-statements to properly embed the font. If not, the reader will use a default font of its own. Also, there is no <text></text> tag. The inline styles should be applied to <p>, or <div> or other valid elements.