Phones are designed for the country they are bought from. Different countries use different signals and networks. Since you have a phone in the wrong country, samsung isn't going to help much.
5g might not work as India might use different signals and frequencies that your uk phone doesn't understand. Your sim service might not support 5g in India, Indian networks might block 5g on non Indian devices. Also of note, using an Indian sim in a UK phone will most likely prevent system updates from working
