Ancient Eden - Chapter 79

Chu He transmigrated into a barren world as a lowly odd-jobber in the Xia clan. He had initially accepted his fate and was ready to spend his life ordinarily and peacefully. Little did he expect himself to suddenly awaken the Checkpoint System which rewarded him for checking into places!

Ding, congratulations to the Host for successful checking-in. For your first check-in, your reward is the Golden Nine Turns. Ding, congratulations to the Host for successful checking-in. For your twenty-one-thousandth check-in, your reward is the Golden Manifestation of Buddha’s Form.

Chu He was certain that the world outside was too dangerous, so he resolved to not leave the book depository until he became truly invincible and peerless, and thus he stayed for a hundred years. A hundred years later, the Tiger clan attacked the Xia clan and planned to massacre countless humans, it was at that moment that Chu He finally showed his hand!

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.

When she reborn, she finally understood; men can never be relied on.
That being the case, she can only rely on herself to win, that
splendid brilliance she yearned for, in this lifetime.

To my scheming Stepmother and ruthless sister, I will
destroy all your backings, pull off your wings, and step on your
arrogance! As for Grandmother whom speaks kindly but has a snake-like heart,
and a father who is hypocritical and exploits advantages; I will tear
off your pretense and cut off your hope! Let’s see how you can still
scheme against me!

Witness her splendid fight against her stepmother, punish scum men,
and create havoc in the imperial court, as she soars with the wind and
rises above the water!

But as for that man who still stands! How dare he play with my heart?

- Description from Novelupdates

Lieutenant Jack Fritz is a self centered American man of German descent. He like many joined the United States Navy in hopes of getting an easy life and easy money. In fact getting money and taking it easy is all he has ever really wished for in life.However life seems to have other plans in-store for Jack as he suddenly finds himself at the beginning of World War 3. Though his fight does not last for long as he is suddenly blown to bits by a missile and sent into the afterlife, but instead of going to heaven Jack is dragged to another place where he is given another chance at life by some fiery demon for a price.Having been given no other chance Jack does as the demon says and earns himself life again. Though he doesn't return to his original world, but a medieval one. With no guidance and no higher purpose given to him he simply decides to do the best that he can within this new world of his. This time he will for sure earn that perfect life of his and possibly a lot more.But little does Jack know his fate is not his own and there are many sinister things in-store for him. Also the world he finds himself in is not a safe or simple medieval world, but one beset by dangers from all sides that are already little by little driving humanity towards its extinction.