Seventeen Again: The Sweet Life with My Family - Chapter 623 - : Save Her

Bai Aoxue, the best mercenary in the 21st century, is accidentally sent back to the Chengxi Dynasty in Great Continent due to an explosion in her mission, and trapped in the first daughter of Prime Minister. After her rebirth, she is set up by her father to marry the 5th prince Jun Yeyan who wears a mask all day long.
In the face of bloodthirsty enemies, discord between brothers, collusion among courtiers and invasion of enemy state, can Bai and Jun resolve the crises? What will happen to their political marriage? How will the fierce battle for the throne end?
With many twists and turns, the book brings you to experience palace revolution, love and hatred thousands of years ago.

- Description from Novelupdates

Here martial arts are no longer intangible legends. They have been passed on from generation to generation and from century to century. After the confrontation with science and technology, they have completely integrated into modern society and all kinds of martial arts competitions are taking place across the country as superiority among scholars are hard to reach a consensus but not as difficult among martial artists!

Lou Cheng has found an unknown cultivation item that fuse with him and help him for the first part of martial arts, the meditation.

Towards his original dream and the glory in his heart, he will advances step by step, becoming the warrior of this modern city and the hero of the era!

- Description from Novelupdates

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.

“Transmigrate as the Final Villain of the novel...” Ark stared at his reflection in the mirror he held. It was Theos Von Fallen, the final villain of his favorite novel.Although he was the final villain and the strongest in the novel, he was killed by the protagonist and his harem in the finale.[Ding. The Heroine Snatching System has started] Ark gave a crooked smile when he read the system message in front of him... “Exchange!” he shouted, unwilling to accept the fate they had in store for him.Trapped in the world of his favorite novel as the most “evil” and powerful villain, Ark, now Theos, will use his knowledge as a fan obsessed with the novel to take away all the protagonist's opportunities.Whether he can become the focus of the whole show or whether a script will dictate his fate, he will decide! He will live as a true villain who doesn't care about anything but his life and his loved ones.