The button combination for 1.4 s2 agent mine throw:
(Hold c-right and c-up the entire time)
Press and hold Z, Then tap A, then tap c-left, then release Z
This is the way I do it in 1.4:
(hold c-right and c-up entire time)
Press and hold Z, Press and hold A, Press and hold c-left, then release Z, A, and c-left at the same time.
the timing is basically to hit Z, wait two or three frames, hit A, then next frame hit c-left. after you hit c-left you can release all three buttons. If you don't hold Z for a few frames before hitting A, the mine won't go far enough to be able to blow up the communications link.
To detonate the mine after you throw it, you have to press R + B at the same time. That seems to be the only way I can think of to detonate the mine on 1.4.
I'm not sure how easy it is to figure out how to do the throw, with the explanation I gave, so if you have any more questions, or if you want me to make a video talking about it, let me know.