Differential, Transmission oil change?

I don't know much about cars but, some say Differential, Transmission oil need to be changed and some say I don't need to change and it is permanent oil.

what is the truth? I need some advice, I have 2020 toyota rav4 with 80,000km.

Should I take it to toyota dealership or any other auto shops fine?

Since it's under 100,000km, is it better to sell it and buy a new car? what is your opinion on this?

thanks for helping!