Immortality begin with Alchemy Grandmaster - Chapter 42: Heart’s Test (Extra Publication, Please Follow!)_1

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 his past life, Ethan Steele was an ordinary man living in a modern world—working a dead-end job, struggling through the monotony of daily life, and haunted by regrets of missed opportunities.At the age of 23, his life came to a sudden, unexpected end in a car accident. As his consciousness faded into darkness, he was sure it was over.But fate had other plans. In the divine realm, the God of Fate watched over the balance of life and death.Ethan's untimely death was a mistake, an anomaly that diverged from the preordained path of his destiny. It wasn't yet his time to die, and so, the god decided to give him another chance.“You were meant for greater things, Ethan Steele,” the god's voice boomed. “To correct this error, I will reincarnate you in another world—one filled with magic, swords, kingdoms, and adventure. You shall be reborn, but you will not remember your past until the appointed time. There is, however, a... complication.”By divine error, the god accidentally bestowed Ethan with the Harem God System without having any idea about it.This system is a powerful, reality-bending system that would allow him to charm and seduce influential women to build his harem, growing in strength and power with each conquest.“Your memories of Earth will return on your seventh birthday. I hope you enjoy your life here in this world”And with that, Ethan's soul was transported to a new world.

Mu Yao is wearing a book.
When she woke up, she became the dark, stupid, arrogant female supporting role in the book.
The male protagonist is deeply disgusted by the stupid and ignorant fiancée Mu Yao who comes out of the mountains and often jumps in front of him.
Until one day, Mu Yao took the initiative to ask him to dissolve the engagement.
The male protagonist thought that he could get rid of Mu Yao’s troubles from now on, but unexpectedly, he somehow became the ugly and stupid dog beside Mu Yao.
From then on, during the day, the aloof male lead sneered at Mu Yao.
At night, after becoming a stupid dog, the male lead curled up the dog’s body, and was pitifully hugged by Mu Yao in Xiangruan’s arms, looking up at the dog’s head, begging to be petted.
The heroine will be beautiful, and the hero will wear his soul on the dog raised by the heroine after dark

Fragment:
Everyone knows that the hero has a fiancée who grew up in the countryside. She is said to be ugly and ugly, and she is extremely disgusted by the hero.
Until in the box, everyone saw the hero squatting on the ground, holding the snow-white slender ankle, carefully putting on shoes for the girl who looked like a fairy, and asked in a hoarse voice: “Yaoyao, when will you follow me?” Am I re-engaged?”
Dumbfounded guys: “…”
Damn dirt ugliness! Damn dislike!

1. The heroine is ugly in the early stage, beautiful and squeamish in the later stage, sprinkled with sugar, and the text is so sweet that toothache
2. If you don’t like beauties, please click X, you don’t need to love, please don’t hurt ~ everyone is a soft and civilized beauty. Declined to pick up the list!
3. The author’s scarf will be worn outside the episode: Beauty Wushuang

Content tags: rich family sweet text wearing books cool text
Search keywords: Protagonist: Mu Yao ┃ Supporting role: Next book: “The Rabbit Spirit Who Became a Terminally Ill Male Supporting Partner”, “The Overlord Hiding in the Female Supporting Pocket”, click on the author’s column to collect it ┃ Others: Daily update, sweet sweet
One-sentence introduction: After the hero is dressed as a dog, he chases his wife every day at the crematorium

- Description from novelbuddy

This is the 40,000th year that the Empire has ruled the Milky Way. The glory of the Great Crusade has long been lost in the dust of history. Su Yu traveled through time and opened his eyes to see the ruined planet in front of him, with a confused look on his face.

On this planet, there are extremely dilapidated war machines that stretch for thousands of kilometers, alien behemoths whose roars can shatter mountains and rivers, and radiation that can cause further damage to the surrounding environment just by moving. Alien beast——

There is everything here except hope.

Regardless of whether he wanted to or not, Su Yu, who had struggled to survive for three years and was inevitably infected with radiation sickness in the end, seemed to be one of the desperate people.

Until his career panel, which allows for unlimited career changes, was finally opened.

“Ding!”

“It is detected that the host has met the prerequisites. Do you want to take up the occupation [Mechanic]?”

“After completing this profession, you can gain professional experience and improve your professional level from daily maintenance, recycling, and assembly of mechanical creations. With each upgrade, you can gain an increase in physical fitness…”

Looking at the old gun parts piled up in his repair room, Su Yu’s eyes lit up like never before!

Many years later, at the core of the empire, at the highest point of the Terran world, the mechanic from the Ruined Star, the Ghost Shadow Blade of the Dead Wasteland, the restarter of the Titan Weapon Plan, the Governor of the Broken Star Territory, the Lord of Mechanical Ascension, the Supreme Throne of the Forge World, Su Yu looked at the torrent of steel coming from below and waved his hand to give the order!

[Our goal is to make the (second) (crossed out) empire great again! 】

- Description from novelbuddy