How do I know which airports have ILS and for which runways?
There are published instrument approach procedures for all airports served by an instrument approach.  These are commonly referred to as Approach Plates.  (In paper form). Your local pilot shop should have them, or you can order online.
Just look in the section for the airport you are going to and all the available approaches will be there.  Browse to the ones for the runway in use, and choose one that matches your equipment capabilities.  That’s the one you should request with ATC.  (After you get your instrument rating of course!)
If you have a tablet EFB application and the appropriate subscription they can be brought up on your device.
Your question about ILS glide slope not being available on the reciprocal runway has probably been answered before, but the best answer is because it requires a separate transmitter, which costs more money, and needs to be justified based on need and usage.  (I.e. Perhaps the runway without GS is favored by winds when weather is typically clear...)