I just learned that it is very easy to give amazon gift card credits

Someone sent me a code and i signed into my amazon account where i can "redeem" the credit by inputting the code there. I don't think s/he need amazon approval.

If cellnuvo is willing to pay, cellnuvo can certainly send me a code like that upon topup.

Yes very easy. You can send Amazon gift cards with codes on them to people's email addresses in a few clicks.