
Explanation:
VNet1: Peered with VNet2 and VNet3
VNet2: Peered with VNet1
VNet3: Peered with VNet1
Box 1: VNET2 and VNET3
VNet1 is peered with VNet2 and VNet3. Also Gateway transit is disabled.
Box 2: VNET1 only
Gateway transit is disabled, so it can only communicate with the connected VNET1.
Reference:
https://docs.microsoft.com/en-us/azure/virtual-network/virtual-network-peering-overview
https://docs.microsoft.com/en-us/azure/vpn-gateway/vpn-gateway-peering-gateway-transit