Technology

Speed is higher on 5GHz and 6GHz because the channels are wider. For every 10MHz of channel width you can get ~100mbps if there is no interference. 2.4GHz goes so far that it is pretty much impossible to get a channel with no interference and speeds suffer for it. 5GHz has much more bandwidth and lower range so you are much more likely to find a free channel to use unless you live in an apartment building or such. 6GHz has even larger bandwidth available and goes even less distance than 5GHz, though not much less, so finding a free channel should be even easier.

Lower frequency have longer distance coverage, higher frequency have better speeds but shorter distance coverage, and here is common wavelengths of WiFi 2.4GHz 5GHz 6GHz, also new WiFi stands adds new features like mi-mo was added in WiFi 5 and something something raycasting WiFi was added in WiFi 6 and i honestly don't know what been added in WiFi 7 but specs gonna be better for sure

If the cause of the poor 2.4ghz range was tons of interference on that band, then maybe. But lower frequencies simply go farther, so 6ghz will always have a lot shorter range than 2.4ghz. Though while it's impossible to change the laws of physics, it might be possible to change the laws around wireless telecommunication to allow it to transmit at a much higher power - not sure if WiFi 7 does.

Pretty sure length is important for penetration. Wait... what were we talking about?