A:AnswerYes, it comes with only one seal. If that seal is not broken you have a new cellphone inside. Without removing that seal the box will not open.
A:AnswerMemory does not affect carrier compatibility. This phone has a pretty extensive list of bands and will work with the major majority of carriers.Other devices may or may not have supporting hardware to function as this phone as far as carrier compatibility.
A:AnswerYou can use this phone with a prepaid plan. I have a mint mobile plan with this phone. The 'Overview' section mentions other prepaid plans that work with this phone, but I'm not sure if plans not mentioned will work. The plans mentioned are: Cricket Wireless, Metro by T-Mobile, Simple Mobile, Total Wireless, Tracfone, Net10, Mint, and H2O