Q: Can someone who entered US with immigrant visa & has already paid the $220 green card processing fee leave US

A: No. If you leave too soon, you can abandon your lawful permanent resident status, especially, if you never get the card in the first place. It can take a while for the card to arrive.

You need to establish yourself as a lawful permanent resident by living and working in the United States, not somewhere else. Stay outside of the United States to go to school, that is meaningfully interruptive, more than 180 days can cause trouble. It is possible to lose your green card if you live outside the United States more than you live inside the United States,

Filing for a reentry permit tells the US government that you were not living in the United States. It also tells the US government that you may be unable to fulfill your obligation to remain in the United States. Most of the year. I strongly recommend a paid appointment or teleconference, so that you get a better grasp of what your obligations are.

There are many people who choose to abandon their lawful permanent residence, because it does not make sense in their lives.

Obviously, it is better to know what you have to do before you come into the United States.

A: Yes, someone who entered the U.S. on an immigrant visa and has paid the green card processing fee can leave the U.S. before receiving the physical green card in the mail. However, they should ensure they have the necessary travel documents, such as a valid passport and visa, for re-entry to the U.S. It's also advisable to carry the immigrant visa foil in their passport as proof of their legal status.