We received more than $100,000 from a foreign person as a gift for a downpayment. Do additional transfers for tuition for grad school need to be reported on form3520 too?

This is a really good question, and I did some tax research on it it for you.  The answer I reached is that you do need to file Form 3520, to report the receipt of the foreign gift(s) in excess of $100,000; but the fact that some of the money received was intended for graduate school tuition has no impact on the filing Form 3520.  Please allow me to explain that.

There is a $100,000 (annual) allowance per individual person (who is the foreign gift giver), before Form 3520 is required).  The $100,000 limit can be breached, in aggregate, by the receipt of several smaller gifts, made by that same person or by related persons, totaling more than $100,000 intended for any one United States individual.

In other words, several gifts of under $5,000 are not reportable, on Form 3520, until they total up to more than $100,000 in any given calendar year.  So, one theoretical way to avoid filing Form 3520, and still literally complying with the law, would be to have the foreign gift giver send $99,999 in one calendar year, and then $99,999 more in the next calendar year . . .  and so forth in a continuing pattern.  It does not matter, for IRS compliance purposes, if the foreign "gifts" were then spent by the recipient on graduate tuition, saved, or otherwise.

That said, you may still want to file Form 3520 voluntarily, even if you do not absolutely have to, just to err on the side of safety and caution.  There is no actual tax due with Form 3520, and if you are talking about a reasonably straightforward gift of money or property from relatives, then you only have to fill out Pages 1 and 6 (Part IV).  The form can be completed manually, and mailed.  Here are links to the form and the instructions:

https://www.irs.gov/pub/irs-pdf/f3520.pdf

https://www.irs.gov/pub/irs-pdf/i3520.pdf

What is the final conclusion, then?  Well, ultimately that depends on what you decide to do, based on the above.  Form 3520 is necessary in your case, for the year in which more than $100,000 was received; so we would recommend that you disclose everything, remembering that there is no tax due, even if the dollar amounts disclosed on Form 3520 increase.  (When in doubt, be cautious when it comes to IRS requirements.)

After all, with no tax due by filing Form 3520, all it costs is a stamp and the time necessary to complete the form.  Fortunately, despite being 6 pages long, it's a relatively easy form, at least with respect to the beginning page, and Part IV on Page 6, which is all that you would need.