I got me some 20 rolls of it for 5 euros. I know that medium/fast films do not age well, but what are my chances with it? How should I expose it and what is the recommended developer for that film?
It's always difficult or impossible to know with expired film without experimenting, as so much depends on the film itself, and most specifically the storage conditions.....some films seem to stay fine for ever, some "go off" soon after the expiry date, and, as SFX100 is somewhat of a speciality product, I'd be cautious about how well it will last.
But if you spend a few minutes on Google, particularly the Ilford site which has the Technical Data Sheet and specific recommendations, you should have a good starting point. (And good old ID-11 seems to be the recommended basic dev. ).
I have some that's probably that old, it hasn't been a problem for me, I last exposed some of it earlier this year. I've had it refrigerated the whole time though.
I process mine in Xtol, but it would do fine any whatever your favorite is. Ilford publishes recommended times for a number of popular developers. It's grainy compared to "normal" films, so a developer like Rodinal would tend to accentuate that. Much depends on how much you like grain.
If it isn't strored in hight temperature surroundings (Mojave Desert), hight altitude/x-rays contaminationed areas
(in a bag outside ISS/ very near of damaged tschernobyl reactor),
humid/hot temperated area (24/7 chineese kitchen)
The whole time since 2011 - if it isn't one of these issues (hope I forgot none)
I'll give you 94% of best characteristics.
It has always been kept in a refrigerator. I had lots of luck with slow film (ASA 50), but not with fast (ASA 400), so I don't know what to expect from this. One other thing, I have never had SFX before. Providing that it is a film with extended sensitivity over the red, how should I focus for it? Should I treat it as IR, or normal BW film?
New out of the box and using a filter like a Wratten 89B (approx 695 nm cutoff), you will get noticeable Wood effect (assuming there is any to be gotten - IR content varies a lot, even with the seasons). I've no idea whether the extended red characteristics might fade faster over time than other attributes. I believe general consensus is the IR spectral sensitivity is so close to the visible range no focus adjustment is necessary. It's worked for me.