Once you have validated or bypassed the restrictions on your OS X Lion DMG, the safest way to deploy it onto an older Mac is by building a bootable USB installer flash drive. Prerequisites
Fixing Mac OS X Lion 10.7.2 DMG File Errors: Complete Troubleshooting and Installation Guide mac os x lion 1072 dmg file fixed
Right-click your USB flash drive in the left sidebar and choose . Once you have validated or bypassed the restrictions