I can write a long paper about "macOS Sierra (10.12) — downloading, installation, history, security, and legal/ethical considerations." I'll assume you want an informative, research-style paper covering background, technical details, how to obtain the installer legitimately, risks of unofficial downloads, compatibility, installation steps, troubleshooting, security implications, and recommendations. If that works, I'll produce a ~2,000–3,000 word paper. Confirm and I’ll start.
Once you have downloaded the DMG, you must convert it into a usable "Install macOS Sierra" app to create a bootable USB drive. macOS Sierra | Specs, reviews and EoL info - InvGate
A: The official InstallESD.dmg for Sierra 10.12.6 is exactly 4.98 GB (5,350,000,000 bytes). If your file is larger or smaller, do not use it.