Question

what are the advantage of connecting electrical devices in parallel with the battery instead of connecting them in series

Answer 1

in series all the devices get off if one is fuse /off
but in parallel each device has its own separate switch
because the current stops flowing in series

Answer 2

1. If any electric device get fused the other working device will not be affected
2. Different electric device need different energy to work so if connected in parallel they can draw energy as they require