There’s suprising a lot of them since the 747 was very popular at its time so Boeing had to upgraded MORE
This Trijet is built to compete with the popular DC-10 and L-1011 this tail would be similar looking to the L-1011 and might haul more passengers, range and payload and years later it wasn’t developed since they would rather build the 747-400 instead and it turned very popular later one
These variants are basically the ultra long haul version of the 747-400 and have more passenger compacity since it was stretched longer but many airliners weren’t interests with this. The similar one like there today is called the 747-8 Which its still in services which most are cargo
Sadly there’s no official picture of it
In short is basically the 747SP Version of the Boeing 747-400 as its gonna have longer range
The 747X Might be similar to the A3XX Program (Now A380) which it will have to be stretched longer and will have more range to compete with it but it wasn’t interesting to most people so they switched to the 747-400ER Instead which Qantas ordered it which Retired this year
Last one is the 747X Program was the 747XQLR Why is the name so long which have almost more range the 747-400 and more improvements to noise with the engines which will be more quiet like todays planes (787) and will have wingtips like the 777 and 767-400ER, then again it didn’t make it to the Market.
That’s all for today folks I hope you see more of these