I'm researching to see what I need to include/avoid in a webpage to be displayed on both modern browsers and also in Android 4.2.2's WebView. I need these questions answered:
I tried to search for this info, but couldn't find any definitive answers.
caniuse.com is what you're looking for. Use the 'show all' button to look back for even older versions. It should have all info you're looking for.
However it's not as simple as does it support CSS2 / CSS3. Some browsers may support some, but not all selectors. You're gonna have to look up each individual tag/selector you want to use.