The Famous Detective of the Red Mansion - Chapter 183: Scheme

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.

(following the boat) When a person who can get random superpowers every day enters the world of pirates and joins the protagonist group, what will happen as a result?

Luffy: “Si Guoyi! Lin Bei, let’s jump from the sky again!” Kebi: “Please don’t!” Sauron: “Be sure to leave Lin Bei’s room at twelve o’clock every day!”

Nami: “This bastard, just let me…” Akainu Sakasaki: “Bastard Lin Bei, turn me back into a man!

The old lady used her ability to come to her aunt once! “Big” boys, come and meet your father! “Lin Bei:!!! This really doesn’t exist!!!

- Description from novelbuddy

Found a suitable body named Bai Xiao. Reincarnating into the World of Elementalists.

“Mission: Overpopulation of carnivorous fish in the lagoon.

Please kill 666 carnivorous fish in order to prevent the destruction of the lagoon’s ecosystem.

Reward: 20 Balance Points.”

“Mission: Forest fire.

Extinguish the fire.

Reward: 200 Balance Points.”

- Description from Novelupdates

Her first encounter with Qin Sijue is an unexpected one. While trying to hide from her pursuers, she accidentally barges into his changing room. Yet, their paths crosses again fatefully—after a fake marriage, she legally becomes his bride. She imagines that they will only interact before the agreement ends, after which they would have nothing to do with each other. However, Qin Sijue comes over with two red booklets—their wedding certificate. “Take them for an appraisal and see if they’re real”.