Can chikenpox cause a swollen lymph node behind ear?

Yes. If there are pox on the face and head, lymph nodes behind ears will get swollen as they fight the infection. Watch for a tender node, red overlying a node, as they can require antibiotics in a complicating infection. Feel better soon!
Yes. Any local infection can cause swelling of lymph nodes in that area. It is not part of a classic presentation but can occur. All the best.
Chickenpox. Yes lymph nodes do become swollen in many parts of the body. They are strategically placed to capture any spreading infection from getting to the rest of the body. Chickenpox is a viral infection and please be aware that a secondary staph infection can also be present in some of the lesions. If the sores are bigger than a nickel you should see the doctor for added meds. .