Can I accept two funded offers from universities and decide later after April 15? I am an international student. I received several offers, but I am interested in two options:

1) Option A: It is my top choice. However, it gave me only partial tuition, so I will need external sources of funding. The resolution of these sources is going to be in June (federal funds), several months after the April 15th deadline. 
2) Option B: It gave full tuition and a monthly living stipend. I am very grateful to the university. 

For both programs, I have until April 15 to accept offers. I have been reading about April 15 Resolution and it has complicated me to make a decision. Since both schools gave me financial aid, I think there is a problem in there about accepting an offer concerning financial aid. As far as I understand, in Option A, if I pay my deposit fee I accept their financial aid. Nevertheless, to attend Option A I will necessarily need external funding. If I don't receive it, I will not be able to attend Option A.

I already have an opportunity to study a graduate program in US (Option B). I would not like to be in the scenario of rejecting a good and safe opportunity and not have external funding, that would mean not to attend graduate studies this year. I would love to go to Option A, but I am restricted to external factors as funding.

Is there any advise you could give me in this situation?
No, you cannot do this.

According to the April 15 Resolution of the Council of Graduate Schools, you cannot accept multiple award offers simultaneously. You are not committed to any offer signed before April 15, in that you can submit a written statement declining a previously accepted offer. But you cannot accept multiple offers before or on April 15, and changing offers after that date requires a written release from the school with whom the offer that was “in force” on April 15.