"I have worn a suit."
Translation:Dw i wedi gwisgo siwt.
Rydw can be used almost whenever dwi/dw i is used. So dwi/dw i is used for statements and questions whereas Rydw i is only used in statements with Ydw i as the question form. If it was a statement and you used Rydw i and it was marked as wrong but dwi/dw i was accepted then you should report it .