1) Difficult, farmore than two. We must assume something fundamental has been invented/discovered 50 years before... For example Hertzian waves, but this needs a more advanced mathematical physics, which needs a genius (maybe Gauss) to get into that kind of mathematics. And Maxwell, too, has to be anticipated by at least 30 years to achieve this. Let's say Faraday does himself plus Maxwell, and generally 90 years of physics are compressed in 40.
Also, in other sciences, for example Gregor Mendel is not ignored but widely discissed from 1869, leading to an earlier discovery of genetics. Same timeline for inner combustion engine; we must assume Father Barsanti and other Tuscans who were working around have the good idea of trying something with oil.
The only problem going this way is that WW1 will be fought with tech from the Sixties, i.e. nukes and ICBMs...
2) Easier, but can be only the consequence of some major disaster hitting all the Western countries. An asteroid, a catastrophic WW1 dragging on for decades reducing BOTH Europe AND America in shambles, a particularly nasty form of Communism taking over and banning most forms of research ("1984" scenario). Otherwise, we must assume less developed chemicals, no discovery of radioactivity, Einstein died in childhood, no Edison...
WW1 would be fought with, say, 1870 tech (the revolutionary weapons would probably be the Gatling gun, smokeless powder and the Zeppelin), and WW2 would be the triumph of the machine gun and the trench mortar.