Alpha's Rejected Mate Returns as Queen - Chapter 577 - : The Celebration

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.

You take up a student career.

Student career upgrade to lv.7

Acquired skills: primary school knowledge, junior high school knowledge, high school knowledge.

You take the college entrance examination,

You got a perfect score.

Your basic occupation has been upgraded to lv.9, and the job transfer system has been activated.

You change jobs to become a scientist, you gain R&D skills

You use research and development skills to get space fortress construction technology

You use R&D skills to gain starship technology.

You are invincible.

- Description from novelbuddy

The price for saving the world is the right to rule it. After saving a faraway land, Lyn Rivers was cast back to Earth. Wanting the admiration, prestige, and glory of saving that realm, she forced her way back. But she was forgotten, and someone else claimed credit for her deeds. Now, with the power of a deity of destruction, she desires nothing more than to claim her place in history. To do that she will conquer dungeons, make alliances, destroy kingdoms, and build an empire. After all, why ruin the world when you can bend it to your will?

Due to the mercilessness of a wicked God, the Demon Queen’s Soul is sliced in half, reincarnating twice in her third life! Unfortunately for her, one of her halves reincarnated as a Living Armor inside the depths of a labyrinth!

Reincaranted not as a Living Being, but as a Living Armor, an Undead Ghost inhabiting a set of rusty armor, she will have to survive within the depths of the labyrinth as a Level 1 Monster!

However, as the former Demon Queen, she will destroy each challenge that dares come her way by relearning all the abilities, skills, and spells that she once held as the Sovereign of all Demons while merging them with the unique powers of an Undead!

As she rediscovers her previous life powers and knowledge, she begins to build a Demon Kingdom from zero, gathering strong allies and going against the Nations that had deemed of Demons, Beastmen, and Monsters as unholy existences!

...However, a dark shadow looms on the horizon, creeping slowly towards her future as she unravels the mysteries of the world and the gods that govern it.

And amidst the chaos of her third life, where could her other half had reincarnated?

Ruthless against her enemies, and compassionate towards her people, she shall reform the Heavenly Laws set by the Gods themselves!

This is the story of the weakest Demon Queen, who has sworn to never commit the same mistakes of her previous lives, and now, she will become the strongest!

An exciting action-filled adventure with Sci-fi, Necromancy, Magic, Fights against Gods, and Kingdom Building!