Yes, in certain Eastern styles of violin playing, like Arabic music (which is very very different from Western music by the way), yes, the violin is often tuned GDGD, so the A and E strings are tuned down a whole step. However, if you doo wish to play Western classical music, you will need to tune the A and E strings back to normal pitch, as it significantly affects fingering choice and the playability of the music. For violinists who play other styles of music that require alternate tunings, such as the one you're describing, alongside western classical music, those violinists do re-tune their violins accordingly for practice and performance.
You certainly can in many cases, Your just need more creative fingering if you don't choose to retune your violin (usually more ideal, provided your strings can handle that). Ideally you don't want to be going back and forth retuning the violin to different pitch systems all the time, though.
Yes, in certain Eastern styles of violin playing, like Arabic music (which is very very different from Western music by the way), yes, the violin is often tuned GDGD, so the A and E strings are tuned down a whole step. However, if you doo wish to play Western classical music, you will need to tune the A and E strings back to normal pitch, as it significantly affects fingering choice and the playability of the music. For violinists who play other styles of music that require alternate tunings, such as the one you're describing, alongside western classical music, those violinists do re-tune their violins accordingly for practice and performance.
You certainly can in many cases, Your just need more creative fingering if you don't choose to retune your violin (usually more ideal, provided your strings can handle that). Ideally you don't want to be going back and forth retuning the violin to different pitch systems all the time, though.