Do not Google "Aion 3.9 download" blindly. Go to server ranking sites like GTopsite or TopG . Look for servers with 3.9 in their title that have been online for more than 2 years. Longevity implies a serious team that verifies their files.
A: No. These are two entirely separate installations. Your retail account is safe as long as you do not mix the bin32 folders. Keep the verified client on a different hard drive partition.
Early iterations of the specialized progression systems before the drastic 4.0 class additions (Aethertech/Gunslinger). Optimization: