回复：皮匠大师said: 签证只要没有被取消，没有到期，就依然有效。....

When your B2 extension is denied, your previous B2 visa is cancelled (被取消) automatically if your B2 I-94 expires before the denial (because you are out of status/unlawful presence in this case-violate the status law/rule), so the B2 visa is invalid . This does not conflict with what 皮匠大师said.