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Where would you put an internal optical drive in the new slimline design of the iMacs today?
Apple removed the optical drive from inside of iMacs to make them thinner and lighter.
Apple, also, removed the internal oprical drive because of recurring reliability issues and premature failures of the internal optical drive all due to both heat reiated issues and its less than ideal vertical orientation inside of an iMac.
Apple put that optical drive inside of its own external enclosure that you can purchase separately, now, here.
As far as USB ports go, the newer Aluminum style iMac, since 2009, always had only 4 USB ports.
If you need more, you will need to purchase the myriad of USB hubs available to expand the number of USB ports you need.
Don't use antivirus software or hard drive 'cleaniing'/'optimising' software, either!
Good Luck!