Aruba training is using physical appliances that are remote-accessible. If you work for a partner, and have access to Arubapedia, you should definitely look for Aruba Workbench which provides remote access to (physical) lab equipment.
The ACMP exam 6.4 has been retired as far as I know, and the exams can only be done on ArubaOS8. So it may not make sense to still study for ACMP 6.x.
AOS 8 has an option to run Mobility Master and controller virtual, just APs must be physical. If you don't work for a partner, please contact your local Aruba team on what they can do for you. Send me a PM (personal message) on Airheads with information on where you live, if you need help to get in touch with them.