I was recently promoted, but I keep making mistakes in my new responsibilities. My colleagues are also much more experienced than me. Should I ask to go back to my original position?

In a healthy work environment, your colleagues more familiar with the tasks in your new role should help you.

But let's work on things that you can control. Why are you making the mistakes? What could help you make less mistakes?

Do you need specific training? Then ask your boss for the training. Or ask your colleagues nicely for help.

Are the new instructions tricky to follow? Sometimes old SOPs passed down from long ago can be confusing. Would it help to set aside time to come up with an updated SOP or a checklist? (Updating such stuff for the organisation could prove to be another boost for your performance review)

Are you learning from your mistakes? This could be very task-dependent so I'm just making general statements. If yes then you're fine, hang in there. If not, i honestly don't think going back to the old role is a good idea because your boss obviously thinks you're better than that. Is there a lateral role that might suit you better? Same "level" of stuff that you're doing after promotion, but you may be better at that. If so, maybe ask for some exposure and consider a transfer?

Don't give up! It is only 3 months. Learn from your mistakes and move on. Continue to learn and you will have more experience in the future. The hawker selling char kway teo also took years to perfect his skills in order to attract the crowd. Give yourself time and space to learn.