查了USCIS的官方规定，有些不太懂，请过来人指点。
1. 最早什么时候申请pre-completion OPT?
A student may file for OPT up to 90days before he or she completes a full
academic year. If the student has already completed a full academic year, he
or she may apply for OPT up to 90days in advance of the requested
employment start date.
问题：什么是full academic year呢？是指寒假那段时间，还是暑假那段时间？现在申
请的话，算哪种？ 要比offer上的开始日早90天么？也就是说，公司给的job start
time至少要在三个月之后了吧，不然不满足申请条件。
2. "Students with approved pre-completion OPT may work up to 20hours per
week while school is in session. Students who are eligible to register for
the next term and who plan to do so may have approval to work full time when
school is not in session".
问题：既然Pre-completion OPT只能工作<20小时，这个一般公司不能用作full-time身
份吧。。 我看到不少人都是用Pre-OPT来做Full-time permanent job，想必默认是
40hours/week，那不是违规了吗？
3. 最早什么时候申请post-completion OPT？
A student may file the request for post-completion OPT no more than 90 days
prior to the student's program end date.
意思是：最早毕业日前3个月才能申请post-OPT.
问题是：如果是PhD，这个end date时间未定，可以是一年中的任何一天。在申请时，
人家怎么知道我哪天毕业？？难道要系里或老板开具证明说哪天毕业么？也就是说，如
果我（Ph.D学生），现在想申请post-OPT，就要要挟老板让我在三个月内毕业？
有点长，但相信这里的每个问题，版上大部分人都将会或已经遇到过，请指点。
