Thank you for trying to include screenshots. There are just a few issues with yours. The one of your app list is just that a random pic of your app list. I specifically was hoping to see the G section where you might find the Gemini app, more to get you to look in the correct location but also to show us if this device is truly missing Gemini. The other image of Google Assistant's app page doesn't show us anything interesting but I will say that none of the things we've talked about or that we are looking for will be found in this location.
Please follow these instructions.
Open your app drawer, usually you slide up from bottom to show all of the apps installed on your device, I assume this works the same on Redmi devices. Find the Google app, you may have other Google apps but this one just says, Google, with the G logo icon. Tap your profile picture to reveal a menu and select Settings. In the list that opens select Google Assistant. Scroll down the page here to find one that reads "Digital Assistants from Google", and tap that. This is where you will find Madd62's screenshot of the page used to change from assistant to Gemini.