Dell N2000 series stacking

Hi,

I have unit 4 units n2048p stacking together as shown, can I force switch 1 become permanent master/management unit? Currently I only can renumber the unit ID. Firmware ver. 6.3.1.8

Additional question:

1.) I have 1 voice vlan and 1 data vlan, how do I enable LLDP on this? 

2.) How should I configure QoS for voice vlan?