3.14. Is it possible to use both LGPLv2 and LGPLv3 licensed libraries in the same application?

Yes, it is possible to use both LGPLv2.1 and LGPLv3 licensed libraries in the same application for example by having these as separate shared libraries. Doing this does not require changing license in either of the libraries, and it is possible to select a proprietary license for the application, if desired.