I got married K1 visa and all, and got my Green Card (2 year temporary) in January 2021. So it’s good until January 2023. I just got a divorce in June 2021. I’m leaving my new born child with my wife in the states. I’m going back to my country. If I want to come back to the U.S. to visit my child, can I use this temporary Green Card to enter the states until 2023? My wife is 100% ok with me coming back to visit our child. The green card hasn’t expired yet. Is it permissible?
It sounds like you're leaving the US because you are abandoning your permanent residence. In that case, you are not eligible to return on the basis of your green card. See 8 CFR 211.1(a), which provides that the green card may be used by someone who is arriving "as a lawful permanent resident returning to an unrelinquished lawful permanent residence in the United States."
Instead, you should relinquish your permanent residence (using form I-407) and apply for a B-2 visa (although this may not be possible these days because of COVID-19).
You should also be aware that retaining your green card means that you are liable to report your worldwide income to the IRS, and potentially pay income tax on it, even if you are not physically present in the US.
If, on the other hand, you intend to return to the United States eventually and resume your residence there, you can indeed use your green card to enter the US, provided you have not been absent for more than a year. Talk to an immigration lawyer before doing this, because there is a good chance that the US government would find that you had abandoned your permanent residence even if that wasn't your intention. A lawyer can help avoid this.
It's not clear from your question whether you are leaving the US because you just don't like to live in the US anymore, because you have the (mistaken) impression that you can't stay in the US anymore, or it's just a brief visit abroad.
If you just don't want to live in the US anymore, then you should file I-407 to formally relinquish your permanent residency, in order to stop being subject to US taxes on your worldwide income. After that, your ability to enter the US in visitor status would be similar to that of any other foreigner trying to enter the US in visitor status. It is not guaranteed and it is always possible you will be denied for failure to overcome the presumption of immigrant intent.
If you want to stay in the US but think you have to leave, it is not true. You are a US permanent resident (albeit a conditional permanent resident), and your status does not depend on your spouse or your marriage. After divorce, you can apply for Removal of Conditions by yourself on the basis that your marriage terminated through divorce. (Of course, that is assuming that your marriage was not fraudulent, but a green card or even citizenship through a fraudulent marriage can always be revoked, regardless of whether you divorce, anyway.) There is no required time frame to file a waiver Removal of Conditions (i.e. one that you file by yourself, e.g. on the basis of divorce). So you can file it immediately after divorce is final, when your 2-year conditional permanent residency is almost up, or even after your 2-year conditional permanent residency is over, up to and including if you are in removal proceedings. Removal of Conditions can be filed while you are in the US or outside the US.
If you are leaving the US for a brief trip planning to return to live in the US, you would be subject to the same conditions as any other US permanent resident. You would need to maintain residence in the US, as determined by many factors. There is no reason why you would be denied entry on your valid green card (if you were gone less than 1 year and the officers determined that you did not abandon residence) just because you have divorced. There is technically a provision in the law allowing the DHS Secretary to revoke the conditional permanent residency of someone who has divorced, but I have not heard of this happening, and I believe that you could still apply for Removal of Conditions in that case. If you are worried about that possibility, I guess it makes sense to apply for Removal of Conditions as soon as your divorce is final.
The situation is addressed in this law.
(b)(1)In the case of an alien with permanent resident status on a conditional basis under subsection (a), if the Secretary of Homeland Security determines, before the second anniversary of the alien's obtaining the status of lawful admission for permanent residence, that-(A) the qualifying marriage-(i) was entered into for the purpose of procuring an alien's admission as an immigrant, or (ii) has been judicially annulled or terminated, other than through the death of a spouse...
the Secretary of Homeland Security shall so notify the parties involved and, subject to paragraph (2), shall terminate the permanent resident status of the alien (or aliens) involved as of the date of the determination.
In other words, the Sec'y must cancel your permanent resident status. There are conditions for delaying, for example
Any alien whose permanent resident status is terminated under paragraph (1) may request a review of such determination in a proceeding to remove the alien. In such proceeding, the burden of proof shall be on the Secretary of Homeland Security to establish, by a preponderance of the evidence, that a condition described in paragraph (1) is met
which only delays the inevitable.
This guidance from the USCIS Policy Manual describes aliens who are barred from adjusting status. It does not appear possible for you to petition for termination of your current status, instead the burden of termination seems to be put on the Sec'y of Homeland Security which will happen in 2 years). This is a result of Matter of Stockwell, where it was ruled that an alien with CPR status cannot change his status.