How to list specific node/edge in networkx?

Suppose one below tree-like structure in networkx graph:

n-----n1----n11
 |     |----n12
 |     |----n13
 |           |----n131 
 |----n2             | 
 |     |-----n21     X
 |     |-----n22     |
 |            |----n221 
 |----n3


      n4------n41
      n5

1. How to list all nodes with "subnode" and its depth, here: n,n1,n13,n2,n22,n4
2. How to list all nodes without "subnode", here: n11,n12,n21,n41,n5
3. How to list orphan node, here: n5 and how to list "orphan" edge, not belongs to root n edge, here n4-n41,
4. How to list node with more than 2 "subnode", here n,n1
5. How to deal with if n131,n221 have an edge exists in nodes traversal, will infinity loop happen?

Thanks.