It is best to install to the default C:\Cadence\ directory to avoid pathing errors.
The most reliable way to get the viewer is directly from the Cadence website. Avoid third-party mirror sites to ensure you are getting a secure, malware-free installer. Cadence PCB Viewer Download Center allegro free physical viewer 174 download link
The viewer is more than just a "read-only" tool; it provides deep insight into the PCB design: It is best to install to the default
Click on any element to see its electrical and physical properties. System Requirements for Installation allegro free physical viewer 174 download link
No. This version is completely free and does not require a hardware dongle or a license server.
This build is highly stable and widely used in corporate environments.