父母5月底入境，I-94已在11月底到期，但他们的签证是多次入境，而且明年五月份才到期，请问：
1. 如果在签证有效期内去加拿大（需要加拿大签证吗？）从DETROIT那边走。再回美国，能把身份变有效吗？
-Because their I-94 expired and they did not leave US, their B1/B2 visa is also invalid automatically. So, they need to apply for the new B1/B2 visa to enter US if they leave.
2. 不久后会过，超期在6个月以内，影响下次申请签证吗？
-They need to leave US as soon as possible if they do not apply for the green card within US. Otherwise their future non-immigration visa application will be afffected.
3. 现在申请延期还能拿到吗？
-They can not extend their B2 status because their I-94 expired.
4. 如果现在申请绿卡，将来可以回国待一年吗？
-You can sponsor their green card application and they do not need to leave US even if their I-94 expired (unlawful presence).
还是只能待少于6个月，否则绿卡有被没收的危险？
-After they get the green card, they can go to China and stay there for less than one year occasionally.
多谢！
