Open a Street Stall and Sell Vigorously - Chapter 1

This is my first original novel, it may be bad, but this is all in my mind and imagination. (Warning!! There will be an Incest genre) Thank you o⁠(⁠(⁠*⁠^⁠▽⁠^⁠*⁠)⁠)⁠o(oh yeah I forgot, this cover is not mine, I just edited it, if you feel you own it and don't like me using it, please tell me)

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.

“I Possessed the Academy’s Silver-Rank Examiner.”I was on the verge of becoming someone who’d be pushed around by students left and right…◎ [Silver Gatekeeper]“No one can pass without the Gatekeeper’s permission.”I awakened an absurdly overpowered trait.TN: This novel follows a protagonist who becomes a rank examiner, tasked with evaluating students at an academy to determine whether they are worthy of advancing from Bronze to Silver rank. Known as the Silver Gatekeeper, he has the authority to decide which students can progress. As a gatekeeper, he possesses overpowered abilities, making him powerful when fighting on the examination field.