Which is better? feeding 7 months baby with porridge of several fruits or with one fruit alternately. e.g only apple, only cherry and so on?

Single to start: This depends on the process.Every new food can trigger a food reaction (vomiting, diarrhea, hives) that might result in hospital level care for dehydration. New foods should be offered one a time, waiting 3-5 days in between new foods. Reactions can occur early or late, so closer timing risks overlap of reactions. If none after 3-5 days, the food is safe and can be offered with other safe foods.