You get a directory in /home with a quota set on it. IT IS NOT BACKED UP.
Hathor has the modules environment to allow you to switch between different compilers and libraries.
Compute jobs should be run through the queueing system so that nodes do not get overloaded. The queueing system will run each job on a set of free compute nodes, copying the output back to a user-specified file at the end of the job. The queueing system is Torque/Maui; this will be familiar to users of the HPCS, but please note that the available queues are not the same. To run parallel jobs you will need to use the appropriate job launcher. That is mpirun.