I've seen that there are now a few creators converting The Sims 4 objects for use in The Sims 2, and I was wondering if anyone knows of a tutorial to explain how it's done? Or indeed any tutorials which may help me to figure it out!? Any links are much appreciated :-)

There are three programs that I know of:
- TSR Workshop, the newest version (works for CC and ingame objects, but I don't have TS4 so I only use it for CC)
- S4PE
- http://sims4studio.com/ (only works properly if you have TS4 installed - I can't get it to work).

So far I've extracted OBJ meshes with TSRW. It's the same method as for TS3 meshes (just open it as a TS4 object - there's a 'is this a TS4 object?' popup, and click 'yes' to it). I extract textures with S4PE (for some reason not all textures show up in TSRW). From there you can convert objects pretty much the same way as you convert TS3 meshes.

No idea about clothes...

It's very easy to extract stuff for use in TS2. You need the OBJ and the textures (as Png or DDS), and you're good to go. From there it's basically just like making any object for TS2. You may have to do adjustments to the meshes to make them fit, particularly wall items (walls seem to have a different placement) and chairs (TS2 chair meshes are placed low) and other useable objects, but for the most part the sizes are mostly the same between the games.

I would want to learn it also, but to get me started I would need a step by step plan, I'm afraid.
For starters, I don't have any idea how to convert TS3 meshes.

If you're only planning to convert static objects, it's surprisingly easy. Clothes and objects that require animated parts are more difficult. I suggest you start with a simple deco object, and go from there, since SimPE can be very overwhelming at first.

You need to already know how to make TS2 objects, but there are a ton of tutorials showing how to, so that shouldn't be a problem.

Thank you! :-) I hope to get started on some conversions over Easter. The main things I want to do, at least to start with, are the fossils - they look so cool, and I'd love them in my game! :-)