In relationships, it is not illegal to lie about your age, but it is immoral. For example: If you are planning on having sexual intercourse with a minor, or vice versa, the lying of the age is...
Yes. Some people just do it to impress people or be on cool websites. But people who do it. DON'T ! If you lie about your age in order to obtain goods or services that you would normally be excluded...
Yes, you are falsifying legal documents. In some states there are specific penalties for getting married under false pretenses and even the individual performing the wedding can get into...