25.3-25.5: Photons don't care about the direction of time. Fire one backwards in time from the detector to the emitter.
31.1-31.2: To avoid the bomb, the light must be polarized horizontal ASAP.
31.3-31.4: A sugar and a rotator in series, or a rotator and a mirror will preserve polarization going one way and rotate 90 degrees the other way. You may have to flip the rotator over by clicking on it.
31.5-31.9: Go backwards from the detector to figure out where the polarization has to be horizontal, and where it has to be vertical. You never need to consider interference.
34.1: Without rotating the polarization somehow, you'll never get enough photons through the filter.
34.2-34.3: Avoid hitting the rock and the top bomb.
34.4-34.5: You only have one option left for reflecting away from the bottom bomb. And you'll need vertical polarization to use it.
34.6-34.8: You can only absorb 25%, and it should be obvious by now which path you have to absorb from. Now arrange glass and vacuum to produce the correct interference.