Once yours is approved it will remain active until it expires, Sept 2019.
Your friend won't be able to renew and will expire on 12/5/2018.
The date 3/5/18 is the cut-off date of all DACA renewal applications ONLY.
Basically, if your DACA expires between now and 3/5/18 then you can send a renewal application, applications will ONLY be accepted for the next 30 days.
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Hoping for a brighter future, one where worrying about my status expiring every two years is far, far behind these heavy shoulders.