The Inheritance Of The Supreme Immortals - Chapter 11 - : The First Inheritance

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.

In a world where kingdoms rise and fall, a seasoned player unexpectedly finds himself transmigrated into the very game he once mastered—Caldera. However, his new life as a ruler comes with a crushing twist: severe debuffs and harsh restrictions on his talents make survival nearly impossible. Against overwhelming odds, he fights tooth and nail to carve out a legacy. Despite his brilliance in strategy and marvels in combat, failure becomes his ultimate fate.

A world filled with heroes with superpowers. A world attacked by calamity fiends. A modern world filled with wonders and dangers.

Shi Xiaobai, a child from normal Earth, walked into such a world, proclaiming to be its king. But at the first signs of danger, he is forced to make a choice, one which he cannot refuse for time would repeat, making him face the choice again.

He is not humble nor is he modest, but neither is he delusional. Yet, the Absolute Choice seems to make fun of him. Will the joke be on him or will he laugh at his opponents? There will be many watching his escapades, and there will be some joining him in his adventures.

To see through the world and to grasp its truth, that is the destiny of the King.

- Description from novelupdates

Fei Bai discovered through his boyfriend’s trumpet account that he had been wearing a green hat. Not long after the breakup, he recognized the third party in their school coffee shop.

The senior brother is handsome and tall, but it looks like… he’s not a 0.

When Fei Bai thought his ex might be doing zero for love behind his back, he became angry. He decided to take the initiative to seduce this senior brother so that his ex-boyfriend could also experience the taste of wearing a green hat.

The sky’s the limit. Fei Bai successfully seduced the third party. He walked side by side with this senior brother on the campus and bumped head-on unto his ex-boyfriend.

He thought the moment of revenge was coming, but in the next second, he learned that he had flirted with the wrong person. The senior brother beside him was not the mistress but the former president of his father’s company!

Fei Bai originally planned to apologize and run away, but he didn’t expect to be blocked in front of his home the next day.

The man he called senior brother pressed him against the wall and said in a low voice, “You are so good at seducing people. Who would let you go?”

- Description from Novelupdates