AppleTV 4k resolution not in settings

Other than the difference between 4th generation and 4K (5th generation), do also consider:

• When you connect the Apple TV 4K to a TV screen, make sure the HDMI cables (Premium High Speed) and devices in between (e.g. AV receiver) also support 4K (HDMI 2.0/HDCP 2.2).
• Some 4K TVs have multiple HDMI ports, where only a select few support 4K resolutions (HDMI 2.0/HDCP 2.2).
• Some TVs need the HDMI ports to be configured for 4K devices.

What is your make and model TV?

you can write your model number for us to verify what version you have

the 4g model don't support 4k only the 4k model does

it's remote has a white circle around the menu button Apple TV 4K - Apple

That is a 4th gen, you will need to upgrade to the 4K model Apple TV (a1842)

Identify your Apple TV model - Apple Support