Sorry, this will not be possible.
For 100Mbit passive POE the unused 4 pins of the 8 pins CAT5(5e, 6, 7) cable are used.
For 1000Mbit passive POE the same pins are used but they are modulated over the data signal.
Using 4 pins only is impossible if you wish to transport POE and data. You probably have some sort of ISDN or analog telephone cable, such cable is not usable for network traffic.
Your best solution would be using local power and getting 100Mbit over the 4 pin cable if it turns out to be at least CAT5 cable.
If you indeed have multiple 4 pin cables you COULD use one cable for the 100Mbit data and a second cable to feed the power over the correct 100Mbit POE pins (manually crimping connectors, etc.) and then inject it with passive POE. But this is very sketchy, prone to failure, unsupported and will definitely FAIL if it’s indeed ISDN cable. And most of all, well, euh, you don’t do it that way.
Do it right, or don’t do it! 