Two galaxies aligned in a way where their gravity acts as a compound lens

One fun thing think about is that these two galaxies are only aligned from our perspective in the universe. Viewed from a different location, and they're just two normal galaxies.

Also, imagine having the technology to send signals through the lens and get the attention of intelligent life on the other side.

I’m sure there are plenty of civilizations that have done this, but on the time scale of the universe no one happens to look at just the right moment.

But wouldn't the size and age of the universe also imply that someone has looked at just the right moment somewhere somewhen.

Don’t radio waves weaken proportionally to the square of the distance? No one would be able to detect them past a (relatively) small distance.

The energy density drops off as inverse square law, but the photons go forever. Radio is just photons (light) so it goes forever until it interacts with something it hits. The expanding universe will stretch it's wavelength slightly however.

Regular EM Radio waves are not photons. Photons have special configuration which prevents leaks into surrounding space, while regular radio waves are just waves.

Nope. Radio waves are made of photons. All EM waves are made of photons.

Radio waves are not photons. Light beams are not photons.

Light beams (or similar sources of EM waves generated by individual electrons or nucleus) are made by photons. We can record individual photons.

Maybe, radio waves are made of photons, but nobody confirmed that yet, so I can safely say «no». If you can confirm that, Nobel prize is yours.

Are radio waves quantized? Of course, at Planck scale.

Is it possible to form a single 100kHz photon using a macro antenna? I hope for «yes», but I have no idea about «how».

Maybe check Wikipedia? Because it refutes you in the first sentence on the articles for "radio", "photon", and "light". You're just being pedantic about word definitions to play games with people.