How do I fix this toilet flange?

In preparation for tiling, I removed the old particle board underlayment beneath my vinyl flooring. The board was water damaged under the toilet and while removing it, the rusty screws holding the flange in place crumbled and the ring fell off with absolutely no effort. The cast iron flange was also disintegrated, and a few parts crumbled off so I don't believe it can be saved. (A plumber installed a toilet a few months ago and told me my flange was in great shape!)

Attached is a photo of the flange that fell off, and the remaining plumbing. I have little knowledge of flange anatomy. How do I fix this? And, should I tile before or after fixing the flange? Should I tile right up to the pipe?

The right way to fix this is to get a different plumber to install a new flange. He should use one with a stainless steel ring and use stainless steel screws to anchor it to the floor. Brass screwswould also work, but brass is not as strong as stainless steel. There are various DIY way to deal with this, but a good plumber would be the best way to go, IMHO.

Thanks. I'll get a professional to do it. That's not a problem.

But should I tile before or after I have someone come fix the flange?

The proper place for a toilet flange is on TOP of the FINISHED floor. This means that the tile is under the lip of the flange, then fasteners go through it into the subflooring. There can be NO gap between the bottom of the flange and the tile...it must sit ON the floor. Now, to avoid drilling holes in the new tile, you can notch where the screws need to go before you set the tile. You need to allow enough space to insert the flange and still have the rim supported so it's best to have the flange, even if it's not installed, so you know the required clearances around the pipe. If the ID of the pipe is 4", you can use an internally mounted flange, then you could tile up to the pipe. Outside is preferred, but inside would work. Don't try this if the ID is 3".

You answered all of my questions. Thanks.