Unfortunately, it sounds like you got universal coil overs. That means the sleeves are intended to fit over a multitude of shocks and intended to be used on lots of cars. This is very common for ebay cheap stuff. What you're suppose to do is use the o-rings as spacers between the shock body and the sleeve (you roll them over the shock body and then slide the sleeve over the o-rings). A quality vericle specific sleeve from a reputable company (Ground Control for example) will fit around a shock like a glove. That's why they cost 200.00 to 300.00 for a set as well. What will eventually happen is that the o-rings will deform and the sleeve will get sloppy and start making all kings of noise. Sorry, this is the downside of cheap parts.
As for the sleeves themselves, my "guess" is that the longer ones are for the front. Sleeves cannot be used on the rear because the focus does not have coilover shocks in the rear and there is no seat on the rear shock for the sleeve to rest on. As I mentioned earlier, most coil over systems that have adjustable rears use a special mount that fits into the existing rear spring perch cup. It has very limited adjustability.