Yes, it is generally safe to introduce wheat and apple cereal to your baby if they are at least 6 months old and have already tolerated moong and rice cereals. Start with small amounts, observe for 3 to 5 days for any signs of allergy such as rash, vomiting, or diarrhoea, and gradually increase the quantity if there are no issues. Please consult a paediatrician if any adverse reactions occur or if you have any concerns.