  We report on the Fermi-LAT detection of high-energy emission from the
behind-the-limb (BTL) solar flares that occurred on 2013 October 11, and 2014
January 6 and September 1. The Fermi-LAT observations are associated with
flares from active regions originating behind both the eastern and western
limbs, as determined by STEREO. All three flares are associated with very fast
coronal mass ejections (CMEs) and strong solar energetic particle events. We
present updated localizations of the >100 MeV photon emission, hard X-ray
(HXR)and EUV images, and broadband spectra from 10 keV to 10 GeV, as well as
microwave spectra. We also provide a comparison of the BTL flares detected by
Fermi-LAT with three on-disk flares and present a study of some of the
significant quantities of these flares as an attempt to better understand the
acceleration mechanisms at work during these occulted flares. We interpret the
HXR emission to be due to electron bremsstrahlung from a coronal thin-target
loop top with the accelerated electron spectra steepening at semirelativistic
energies. The >100 MeV gamma-rays are best described by a pion-decay model
resulting from the interaction of protons (and other ions) in a thick-target
photospheric source. The protons are believed to have been accelerated (to
energies >10 GeV) in the CME environment and precipitate down to the
photosphere from the downstream side of the CME shock and landed on the front
side of the Sun, away from the original flare site and the HXR emission.
