Vlan-1 management Vlan/ native Vlan

[spice2003]

Hi

I'm trying to understand the purpose of vlan 1 in hp switches.

I know that untagged traffic goes through vlan-1, what it's mean in HP switches?

let's say i have layer-3 switch with Vlan 10 - sals Vlan, and vlan 20-voice, and then im doing on the layer-3 switch:

vlan 10 untagged A7

vlan 20 tagged A7

some layer-2 switch is connected to port A7, and i the layer-2 switch im doing:

vlan 1 untagged 48

vlan 20 Tagged 48

that's will traverse vlan 10 traffic and vlan 20 traffic in the layer-2 switch, i used vlan 1 and it will make mismatch error but it still work.

now on Vlan-1 users traffic will be transferred and also management traffic like LACP, stp, etc?

need to use vlan 1 just from management?

maybe i need to do:

on the layer-3 switch:

vlan 1 untagged A7

vlan 10 tagged A7

vlan 20 tagged A7

and the same thing in the layer-2 switch? 

thanks a lot