then it is a different story, a frog in the pic looks like a baby, no more then as Grif said 2-2,5", but 4" is a normal size for a adult male. when we see pics like that and people are saying he is 8month old and calling, we will tell you right away it is not normal and he is stunted. see that is why it is important to answer "trouble" questions and post recent pics, only then we can help, people tend to forget or skip something, but this way we get the whole picture, sometimes something little may cause a lot of trouble.

Grif and Carlos answered your Qs, for your Q about growth, if you get a frog at the size 2" and you have 4" frog now, you have your double size and with that normal sized pacman having said that I would adjust his food, mealworms and superworms ( morioworms) are not good at all for pacman due to high chitin amount, superworms have less chitin, but they are very fatty.
african beetle larvae not sure, never fed or saw nutrient analysis, can't say, but usually these types of larvae are very high in a fat content, thus not good for a pacman too. I would skip mealworms/superworms completely and add nightcrawlers ( earthworms) to the diet.