A: Absolutely. Install them in different folders (e.g., C:\Arduino-1.8.57 and C:\Arduino-2.x ). They use separate preference folders ( Arduino15 vs ArduinoIDE ), so they do not conflict.
Wait for the download to complete. You now have the official, untouched installer. Download Arduino IDE 1.8.57 for Windows
: Ensure you allow the installer to add USB drivers, or your board won't connect. A: Absolutely