After Entering the Wrong Room, I Became Mr. Feng's Wife - Chapter 15

At a low point in his life, Xia Ruofei discovered that a scroll that was passed down in his family had a hidden secret: it contained its own independent world.

In the space, there was a spiritual pond that enhanced the growth of plants. There were mysterious spiritual flowers that could cure illnesses. Time in the independent world flowed at a pace ten times that of the outside world. Everything he planted there was of supreme grade and grew at a rapid pace. Everything he raised gained sentience.

From that day forth, Xia Ruofei began a different, brilliant life of planting succulent plants and vegetables, raising animals and flirting with beauties.

Liu Changgong time-traveled to a cultivation world. However, without any talent for cultivation, he was destined to be an average person. So, Liu Changgong simply cultivated for fun. When he was free, he would also do calligraphy, paint, play chess and the qin to pass time…

“There are no heroes. In life, the monsters win.”

...

In 2106, [Mayhem Online], a fully immersive VRMMO game, was released. Soon, it dominated the world's economy when people could exchange the in-game currency with real-life currency and vice versa.

In the year 2107, Flynn Grey, a 22-year-old college dropout with an ambiguous history, joined in the fray of billions of people that had already started playing [Mayhem]. Hoping to uncover the game's secret and earn a fortune, he spent months on adventures without fruitful results.

For better or worse, Shura, Flynn's in-game character, ends up in a great Wyvern's den, acquiring a hidden class and a monstrous race. Join him as he defeats his past and paves his way into becoming a true legend in both worlds.

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.