-As length as you want.
(2)我的護照在今年7月份就要過期了,我想去紐約領館換新護照,一旦換了新護照在舊護照上的I-94是否就無效了,我的身份是否就不合法了??
-Your I-94 duration is not affected by the passport renewal. You can remove the I-94 card from the old passport and store it in a safe place.
(3)我太太想換成F1,在學校是否就可以轉換,是否需要找律師??
-Not to waster your money. Just do it by yourself. It is very simple.