If native VLAN 20 wants to communicate with VLAN 20 through a trunk link what happens? Will native VLAN be able to communicate with VLAN 20?
The "native" VLAN is simply the untagged VLAN on a trunk where VLAN membership is implied. Accordingly, there's no difference between the native VLAN x on a trunk and VLAN x elsewhere.
Whether or not a device also accepts tagged frames with the same VLAN ID that is configured as that interface's native VLAN depends on its implementation.