Tomodachi no Imouto ga Ore ni Dake Uzai - Volume 4, Prologue

A scientific genius named Thomas Harrier was transmigrated to an imperial prince body after a car accident that took his life. He found out that he is in a world similar to our own with a timeline akin to early twentieth century. The body that he is occupying was the imperial prince of a failing empire who suddenly rose to power after a successful assassination attempt of his father. Unaware that the attack is just the beginning of what is to come. He faces many challenges throughout. Will Thomas Harrier be able to live his second life in peace while running an empire and getting it back to its former glory? Or will he succumb into a conspiracy lurking within the country's borders?

Expect some:

Cold war era techs.

Super battleship with advanced electronics, propulsion, and fire control systems?
Helicopters?
Missiles?
Modern medicines and equipment?
AC-130?
A nuke?
Challenger or Abrams or Leopard?
F-4 Phantom or MIG-21?
Colored TV's.

Everything!!!

PS. Cover not mine, I just found it on google.

[Ding, your frog was afraid of your death, so he went on a trip overnight and stole a shelter for you! 】

…

Reborn into a world of global catastrophe apocalypse.

In the face of global recovery, zombies, fog, meteorites, prehistoric creatures, glaciers, earthquakes, acid rain and other devastating global disasters, the only thing Ye Su has to do is to survive.

Unexpectedly, he got a traveling frog when he arrived. The frog was afraid of Ye Su’s death, so he simply stole a shelter!

Ye Su: “???”

But what’s even more outrageous is yet to come.

[Ding, your frog is afraid that you are not stable enough, so he stole the source of fire for you]

[Ding, your frog was afraid that you would be bitten, so he stole the antiviral potion overnight! 】

[Ding, your frog stole the Zanpakutō for you! Additional Asura – Blade Skill! 】

So, when everyone was avoiding zombies, disasters, despairing for food and water, Ye Su had already carried a big knife, drove a car, and came out for food!

- Description from novelbuddy

Ronald Kuangge transmigrates into an urban novel called “The Dragon King in The World” as a Rich Second-Generation that has to properly play his role as the Villain according to the plot in order to return back to earth.After finishing his villain role accordingly to the plot however, instead of going back to earth he has dreamt so long of doing, he ends up going back to the beginning of the story where he has do everything over once again.So in order to go back to earth, he has to act like a villain according to the story once again.Little does he know this time however, the heroines have also regressed back as well...

Traversing into a Fantasy World, Watson became the youngest son of a run-down baron, ranked eight in the family.