Summary
From the port on which the PC and IP phone reside, you can receive two types of Ethernet frame (that is sent from Phone or PC):
When an untagged packet is sent by the PC attached to the IP Phone port, it will be propagated only to VLAN 101. This is because when we added the port 3 to VLAN 101 the Mode option was specified as untagged. While for the other VLAN (101) the option Tagged was selected for port 3 in VLAN 101. Tagged packets will thereby go to VLAN 100 while the untagged will go to 101.
When a packet originates from an IP Phone it is tagged. Since the option 'untagged' is selected for port 5 in VLAN 100, the 802.1 tag is removed before the switch forwards the packet to this port. Similarly, when an untagged packet is originated and sent by the IP Office, the switch will tag the packet before forwarding LAN port 3.