Xyphoe did find two years ago an exploit, also found Green Beret, to easily finish levels in the Robocop game. He is doing it in this new video. This exploit can also be done on a ZX Spectrum, in both computers only the levels 1 and 3 which are withough heights. So you just have to keep 4 enemies behind you, and you will have no boss at the end of the level.
Reading commentaries of the video is interesting as the one by Roi Eclair who wrote : here's actualy another exploit you can do to get infinite energy, but so far i've only been able to do it with the bikers. you need to be almost dry on energy, and kill the biker right when he will hit you. you'll be out of energy, but still alive, and able to end the level taking any more amount of damage you want within the remaining time allowed. found this one by pure accident when i was a kid back then. may not be that easy tu pull, but once you get the right timing, you can be invincible. works on the cpc version, never tried on specy.
For Green Beret, as there are at most 3 sprites of ennemies plus yours, just find 3 ennemies going the same direction than you and you can go to the end of the level easily.