Thank you very much Mr. Pasotti and Mr. Boisteault for the reply.
Following Mr. Boisteault recommendation, I am already setting QGIS_PROJECT_FILE, but this variable points only to .qgs file (default). Instead of pointing to a file, I tried setting a directory to QGIS_PROJECT_FILE, as: /home/qgis/projects/ or /home/qgis/projects/* or /home/qgis/projects/*.*, but no success. In this case, I think we will need to set QGIS_PROJECT_DIRECTORY instead of a file.
Now, according to MR Pasotti, I am already struggling while working on mod_rewrite. Find below my attempt without success: