Cypress does not guarantee any functionality or performance as per the datasheet if the device is operated outside the operating voltage range. The device may work but we cannot say for how much time you will be able to use the device. You may read our app note which may provide some information to you
Yes, the device CY62167G30 will be 3.3 V part and are same as CY62167G parts. The part CY62167G18 will be 1.8 V part while CY62167G will be 5 V part.