I brought my i-mac from Ireland in Bangladesh but while I started to reinstall maverick it says this service is temporarily unavailable. Now I am trying to boot it from USB but while I press option or C it doesn’t boot from the usb that is perfectly

I brought my i-mac from Ireland in Bangladesh but while I started to reinstall maverick it says this service is temporarily unavailable. Now I am trying to boot it from USB but while I press option or C it doesn’t boot from the usb that is perfectly dmg file loaded for installation[SF1] .. The recovery hd only appears. no startup disk. But when I choose startup disk after booting, the startup disk doesn’t load anything to show. What is the problem? How can I solve this?