Hi there, congrats on the new crestie!
Question1: The answer is yes. However, your crestie will grow at a slower rate due to a lack of protein. If you wish, you can give gargoyle gecko diet which has a bit more protein than CGD. If you wish to use crickets here and there, your crestie will grow faster and you get some entertainment of watching your gecko hunt.
Question 2: Since your gecko is so small, it might take a few unnoticable licks from its food. What I do it use a bottle cap and just fill the bottom so its the size of roughly a dime. This way you may be able to tell if the gecko ate any food because the circle should be looking like a moon kinda. Adjust the amount afterwards when you see how much your new gecko eats.
Make sure to mist your enclosure, this is where your gecko will drink water, over time it may learn to drink from a water dish. One more thing, if you are offering CGD and babyfood, your gecko will most likely prefer babyfood because its sweet. I would supplement the baby food with some vitamin and calcium and try to switch over to CGD alone. Best of luck and post more questions if you have any.