Hello i want to integrate reader SDKs in IOS i want to know to work with reader SDKs in sandbox environment do we need real reader device.
Unfortunately Reader SDK currently does not support sandbox mode, so you’ll need to make real transactions. You can test using cash if you don’t want to use a real card; otherwise you would need to do a refund.
Does the Reader SDK support sandbox mode yet? We really want to be able to test transactions on Square Readers using sandbox mode.
At this time Reader SDK doesn’t support sandbox mode. 
Does this mean that we’re paying real fees for development work?
If you refund the payments then no fees will be charged at this time.