a. Group 2
a. The current highest numbered element known is Oganesson with an atomic number of 118 and it's the last period 7 element in group 18 (Noble gases). The hypothetical element number 120, would be the 2nd element in period 8 and the described electron configuration matches other group 2 elements such as Beryllium, Magnesium, Calcium, Strontium, Barium, and Radium.
b. The hypothetical element would be quite similar to the other group 2 elements which are the alkaline earth metals. The element would be expected to be a bit more reactive than Radium.