The headphones will fit. Both phones have 3.5 mm headphone jacks. Almost every pair of head phones is 3.5 mm.
Any 3.5 mm headphones will fit into the headphone jack. As long as the beats headphones are 3.5 mm headphones, which they probably are, they will fit.
Apple Inc develops and designs iphone 5 headphones together with the smartphones.
No, The case won't fit. The iPhone 4 screen is 88.9 mm (3.5 in) while the iPhone 5 is 101.6 mm (4 in).
No. The iPhone 5 is physically bigger than the iPhone 3GS.
No, the iPhone 5s, iPhone 5c and iPhone 5 do not fit into the same cases.
No it won't fit. An iPhone 5C and an iPod 5 are the same size but the iPhone is thicker.
Yes the case will fit. All iPhone 5 models are the same size.
It depends. If the iPhone 4 case is for the GSM model (AT&T) then you can put it on, but the ringer slide button will be partially obscured. If the case is for CDMA models (Verizon) then yes, it will fit because when Apple made the Verizon iPhone 4 they upgraded it to be slightly different, and that is the shape all iPhone 4S's are now. iPhone 4 are very similar in shape with iPhone 4S. If you really want, you can put the iPhone 4S phone into a iPhone 4S case. but it may seems no good in apperance, as they are not exactly same.
iphone 5
No, the iPhone 5 is a little bit thicker
Yes, the iPhone 5 is lighter than the iPhone 4. The iPhone 5 weighs 3.95 ounces (112 grams), while the iPhone 4 weighs 4.8 ounces (137 grams).
The iPhone 5 is shaped differently than the iPhone 4, so the case would not work. It may fit, but it wouldn't be as snug as a fit as you would want. It is usually better to buy the case for your specific iPhone.