If you overstayed and left while you were under the age of 21, it does not matter because you had not accrued any unlawful presence time and, thus, are not subject to the bar to reentry.  If y

No, they should still admit you. Make sure that your passport is valid for more than six months also. You need to bring the original I-20 as well.

Hello. You must wait 5 years to file based on your information. It is 3 years if you got the green card through marriage to a US Citizen. You can file 90 days before your 5 years of Residency. Best

Hello. You may do exactly what you are proposing.  You will need the new original I-797 approval and some paychecks to substantiate that you are currently working with the new company B.