I just want to make it clear that this version of Lemmings on the Master System (rom submission 2) cannot be completed. I breezed through it until I encountered level 24 of Taxing called ''Take A Running Jump'' which asks for 90% to be saved and only gives you 20 bridges to select, the exit is below a huge pit and there is no way to get down there without a digger, floater or a bomber at least.
Sega Four Level 21 of Taxing can indeed be completed as discovered originally by Pooty, it has extremely low video memory so the less terrain you dig and bash through the better.
After I found out that level 24 of Taxing cannot be completed I gave up playing on any further. I know they're only testing levels but you would think that they would all at least be able to be completed one way or another.