Answer: No lo he (HECHO) todavía.
Juan y yo hemos (ESCRITO) una carta.
Step-by-step explanation:
It's "hecho" because "hechido" is not a word.Neither is "hacerido" or "hacido".
It's "escrito" none of ther other options are actual words either.
Both hecho and escrito go against grammatical rules because they are part of the exceptions to verb rules.