VERIFIED SOLUTION i

How to find out if you can use 'repeating data' with a datapush in EngageOne 2.x

Product Feature: Web Service (API)
That is not possible in EngageOne 2.x. The feature was introduced in 3.0.

You can handle simple kinds of repeating elements using ListMap, but I do not think that could be massaged to work with actual repeating groups.
UPDATED:  November 8, 2017