The R242 as it is currently represented on Travel Mapping ends at the access road to Malin Head. However, Google shows it as ending in the nearby small village of Slievebawn/Slievebane. A quick search through theClassification of Regional Roads Order 2012 shows that it officially ends at "Portmore Pier Road, Slievebane" which appears to be about
here.
Donegal County Council's official map also points to the road ending in this location. In addition, the R2D2 sign has been placed in this area, as opposed to Malin Head (although this is not a particularly reliable source!) I feel the evidence in favour of the road ending in Slievebane is far greater than the little to none in favour of it ending at Malin Head.