I do not recommend the General Motor diet per se, but to reply to your query, no you cannot have chappatis on the 2nd and 4th day. Instead of banana you could go with chikoo. And plain chicken, not a sandwich, is your substitute to beef.The diet does not contain any carb from rice or chappati or bread. If you modify the diet to your own version you can lose a small amount of weight but gain it all back and cause severe damage if it is not planned properly for you. Please have a modified GM planned by a qualified dietician to suit your body type and activity levels.