51 and 56 are both EB5 principal beneficiary; 1 is though consular processing, whereas 6 is through Adjustment of Status. I5 is the same as E5 but conditional; EB5 are conditional for the first 2 years, and then after they remove conditions, they become non-conditional.
I56 after ROC becomes E56. I51 after ROC becomes E51.
I was incomplete in my previous post. EB5 conditional permanent residents actually have 4 types: C5* (employment creation, not in targeted area), T5* (employment creation, in targeted area), R5* (investor pilot program, not in targeted area), and I5* (investor pilot program, in targeted area). All of these become E5* after Removal of Conditions.