a) Is His avatar or birth true or false? He is in this world just as we are or Arjuna was there. Is His birth real like ours or is it a magic or illusion? Sri Krishna tells His avatar is true.
b) Is He born with His greatness and Power or without? Swami Desika says He is born with ajahatswaswabhavatha. Jahat means relinquish or without. So ajahat is with or fully equipped. In every avatar He is with full powers and with none of His greatness wanting.
c) Is He born like us with blood and bone, that is with the five elements which have the three qualities of satva, rajo and tamo gunas? Sri Krishna tells that unlike our bodies, His body is full of satva quality alone and is called suddha satva mayam. That is it is not contaminated by rajo/tamo qualities.
d) Is He born because of karma as in our case? No says Sri Krishna and continues that His birth is at His will and determination [sankalpa]. No one else including karma can decide His avatar.
e) Who determines His time of birth? In our case as our papa/punya ripen our births are timed. Sri Krishna tells that His birth happens whenever there is danger to Dharma[righteousness] and Adharma flourishes.
f) What is the purpose of His birth? In our case, we are born to expend the papa and punya acquired in various births. By suffering we spend away our papa and by enjoying we spend our acquired punya. The Lord also in many avatars appears to have suffered and enjoyed. Sri Krishna replies that He is born to protect sadhus or good people , to destroy evil and wicked persons and to establish and maintain Dharma.
These six replies form the secret or rahasya of His avatar. Though He also appeared on this earth like us and played and cried, He is much above and we can never think He and we are same.
We will see sloka 5:
bahuni me vyatitani
janmani tava carjuna
tany aham veda sarvani
na tvam vettha parantapa
"The Personality of Godhead said: Many, many births both you and I have passed. I can remember all of them, but you cannot, O subduer of the enemy!"
Paranthapa = destroyer of enemies [Arjuna], bahuni = many, janmani = births, vyatitani = have happened or passed [to Sri Krishna], tava ca = like you [have spent so many births], Arjuna. That is just as Arjuna thinks his birth now and his births earlier are all true, Sri Krishna's many avatars are all true. Tani sarvani = [but] all the births [of Arjuna and of Sri Krishna], aham =I [Sri Krishna], veda = am aware or knowing, tvam = [but] you [Arjuna], na vettha = do not know or unaware. Thus similarity between the Lord's birth and ours is, just as our births are true, so also the Lord's avatars are all true. Just as we had so many births, He also had many births. But, we do not know our past births. The Lord not only knows His past, He is fully aware of everybody else past, present and future births. Instead of a mere answer to Arjuna's question, that His birth is true, Sri Krishna tells that just like Arjuna's birth His birth is true. Because, everyone knows Arjuna and so keeping him as example, Sri Krishna tries to explain His birth. We should also remember that since the reply says that His births are many, we should never think that His avatars are only ten and All avatars are true.