How PODs can support multiple network using single interface?

Question

In K8s by default PODs come with single interface ("eth0") using Calico CNI, Wave CNI, etc., but then we go for Multus to have multiple interfaces ("net0", "net1").

My question here is "Can we go with single interface ("eth0") always and can connect to multiple networks?" in K8s using route, if so how can we achieve this?

For example: In laptop we always see single interface and I can connect to all DEV network and if permission granted I can also access QA network or HR network by ip-address remain same; The network administrator provides access or permission to get access to required network;