High-order meshes and solution with VTK Lagrange cells

[CsatiZoltan]

For compatibility reasons, our simulation codes interface with unstructured VTK meshes, possibly containing high-order VTK Lagrange cells. To visualize the solution with GLVis, I have the following questions.

1. Are in-memory VTK meshes supported in GLVis (i.e. when GLVis is listening to a port)? The same question, but for the MFME format. In our application, file I/O is prohibited.
2. In VTK, field values can be assiciated with the nodes of the mesh. The -mflag in GLVis only fetches the mesh, while passing the same .vtu file to -g as a grid function throws an exception. Can GLVis extract solution values from .vtu files?
3. Mixed meshes (e.g. Q2/Q1 cells), essential for p-refinement, are currently not supported in the VTK file format. Are mixed cell types inherently unsupported in GLVis, or they are not implemented just in the VTK reader?
4. What are the plans for the support of VTK Lagrange cells in GLVis in the future?
5. Is deep knowledge in the MFEM architecture, in C++ or in graphics programming necessary to implement the features written above? Or would you rather recommend me to work with the MFEM mesh format?
6. A search on Conduit in the MFEM repository makes me think that it is already implemented. Does that mean that it is sufficient to provide our custom mesh data structure and solution as a Conduit blueprint and GLVis/MFEM takes care of the rest?