Hello, I've been offered to buy an iPod Classic, brand new completely factory sealed but its manufacture date was May 2014, will the battery still be alright?
Chances are good that it's stone dead. Generally when an iPod sits around for a few years with no use, the battery craps out. Those sealed new units from years ago are generally only a good purchase if you're a collector. If you're looking for an iPod to actually use, go for a nice used one.