Yes to both. https://www.dcnr.pa.gov/StateForests/FindAForest/Susquehannock/Pages/HorsebackRiding.aspx I highly recommend checking out Cherry Springs state park of there is a clear night with no moon.
Yes there are horse trails. It does not matter where you are from. The Pennsylvania Visitors guides are always helpful for info. There are camping areas available that can accomodate trucks and trailers.
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