IPS 4.3 compatibility skins

[angelbot 0]

are skins 4.1 compatible with 4.3?

[Decon 6]

Yes and no.

One of the things IPS did between major builds (4.1->4.2->4.3) is changed some of the function names internally that the theme templates use. That would be the biggest issue trying to use a 4.1 theme on a 4.3 site. If you know what you're doing, you can go through and manually update all the templates to the latest function names and all that. If you don't... well, you can try and find an upgraded version of the skin by the author.

The other thing to remember is IPS does more than just change function names between major builds, sadly I'm not too familiar with every change IPS makes so just changing function/variables names to match the latest ones may not make your theme act as it should but would get rid of any template error blocks on your website.

I recommend looking for the latest version of the theme by author if you can find it, or looking into the IPS documentation/development guides for how to upgrade your themes to newer versions of IPS. They would probably outline most of the changes you would need and if IPS is still as friendly about their documentation as they used to be, they should be open to the public and you don't need to have an IPS license to view them.

[+IamKangy 38]

I would not recommend it. It can cause some serious issues on your site using an outdated theme. Find the updated version of theme you want to use and you won't have a problem. 

If you do decide to try it must be very clear that you back up both your files and database prior to attempting to use an older theme version.