MTL - Gold Lord is Very Busy - Chapter 37 Vacation

Elena, who spent her entire life as a cold-blooded female knight to avenge her family, ended up dying without claiming her revenge. When she opened her eyes she found that she went back into the past. By day she was a lady in a dress, and at night she carried a sword to change history and prevent her family’s destruction.

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.

The world where the Hero and the Demon King continue to oppose each other. The grand magic from the Hero and the Demon King cross over worlds and exploded in the classroom of a certain high school.

The students who died in the explosion will be reincarnated in a different world. The protagonist, who had the lowest reputation in the class, was reincarnated into a spider. Nevertheless, she adapted quickly to the present condition with strong willpower.

This is a story of she who has become a spider trying whatever she can to live.

Spot was summoned from his comfortable charging pad and familiar floors to a world of magic and intrigue. After the flight of his new patrons, he is left to care for a filthy castle. During his quest to keep this new home clean, he will face demons, foreign armies, and the dreaded stairs.All those who stand before him will be swept away. Those who follow his spotless trail will find enlightenment, purity, and a world on its knees.Follow this wholesome vacuum on his quest to power.