问题1：F1先批准，H1B后批准。这种情况不需要出境，H1B沿用F1签证的I94吗？
-No. The H-1 approval will have the H-1 I-94. If it does not it, then you need to go to China to get the H-1 visa as I memtioned before.
问题2：H1b先批准但没有I94，这时withdraw F1，是不是从withdraw之日起就开始算非法居留了，因为新的H1B尚未激活，而F1 pending状态也终止，所以没有合法居留的身份了？
-Right. You have to leave US to get the H-1 visa in this case.
问题3：我自己正在申请F1，假如我的F1未批复时我们一家离开美国，我的F1申请就作废了，我本人不打算变回H4，真的打算去读书的。
-If you want to be the F-1 student, you may not leave US during the F-1 pending. If you have to leave, then you can apply for an F-1 visa to come back (do not need care about the pedning F-1 application in this case).
先生的H1b先批准但没有I94，先生一个人带两个孩子回去实在很难（因为儿子很小），如果先生一个人先回中国，两个孩子和我留在美国，直到我的F1结果出来，我再带他们回国办理，会有什么问题？
-You may just go back to China together with your spouse, and then they apply for H-1/H-4 visa, and you apply for F-1 visa in this case Talk to your school International Student Office before you leave US if you want to apply for F-1 visa.
问题4：H1b先批准且有I94，需要withdraw F1申请，论坛查到说withdraw也是像正常申请流程一样，从提交之日计起2.5个月才有结果！那我是否需要在收到新H1b受理的receipt number就马上提出withdraw F1申请，还是等到拿到H1B的结果再withdraw F1（这两种做法会有什么区别呢）？
-If withdrawal of F-1 occurs before the H-1 is approved, your status will have a gap, and the H-1 approval will have no I-94.
问题5：记得F1申请时有说明如果受理期间出境则申请自动生效，如果先生拿到H1b+I94马上跑去邻近的温哥华转一圈，那还需要withdraw F1申请吗？
-Technically, not need unless USCIS make a mistake (someitmes it happens).
拿到新的H1b+I94后，离境再入境，需要办理什么手续吗？
-Get the new H-1 visa to come back unless you go to Canada or Mexico and return to US within 30 days. Bring all the H-1 visa application docuements with you.
