The Weapon Genius: Anything I Hold Can Kill - Chapter 34: The Weight of a Crown

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.

After announcing it will be discontinuing all service, the internet game ‘Yggdrasil’ shut down… That was the plan, but for some reason, the player character did not log out some time after the server was closed. NPCs start to become sentient. A normal youth who loves gaming in the real world seemed to have been transported into an alternate world along with his guild, becoming the strongest mage with the appearance of a skeleton, Momonga. He leads his guild ‘Ainz Ooal Gown’ towards an unprecedented legendary fantasy adventure!

If there was an object that could grant any wish you wanted, what would you ask for?Most would ask for wealth and prosperity, while those who are sick would probably ask for health and safety.It sounds impossible, but what if something like that actually existed?...Kirigaya Yuuya, a corporate slave, found himself in an unimaginable situation.After doing a good deed for a beggar, he was given a magical candy that supposedly granted wishes.At first, he dismissed it as nonsense, but when he jokingly wished to be reincarnated as the pathetic character Arthur Vanitas from a fantasy novel he had read, he was stunned to find that the wish had come true!Fear and panic set in as he realized the fate of Arthur Vanitas was a miserable one—he was nothing more than a stepping stone for the protagonist.Just as despair started to overtake him, a voice suddenly echoed in his mind.[Ding! The System of a Thousand Worlds is ready to assist you!][By completing the challenges and missions in the selected book worlds, the system guarantees a change in your fate!][Mission 1: Complete the world titled “Rise of the Unwanted Queen!”][Reward: Mastery of the Five Elements Talent and other mysterious rewards.][Mission 2: Complete the world titled “The Destruction of the World by the White Mage.”][Reward: ...]And with that, Yuuya's journey to change his fate began.

When the eldest prince Luo Fei reached 18 years old, the database automatically screened the genes of omegas across the entire empire for matching. The only son of a wealthy businessman, Mo Lin, had a gene match of more than 90% with the eldest prince. However, the moment he saw Mo Lin, Luo Fei learned that this omega is a sick child with paralyzed legs, hemiplegia, and severe mental illness???