US Immigration from Uruguay

Is anyone facing delays in the approval of the I-829 (removal of condition on Investor immigrant EB-5)

I am a US citizen over 21 years of age. Can I petition my sibling (who is currently 15 years old) via I-130? I know it's faster if my parents immigrate but they are not interested in doing so. I realize my sibling will have to wait 10+ years and I'm fine with that. I'm just wondering if he has to be of a certain age for me to be able to file a I-130 on his behalf? Also, must he remain unmarried the entire waiting period?

My step son has a valid PR status. In Oct 2019 he went to uruguay with the intention of returning to the USA within 6 months. Due to fears of travel during covid, he has been delaying travel and now its been a year and a month. He has a ticket for this weekend to return, will they deny him entry to the USA? Normally after a year you would need to get a new visa but are they being at all flexible due to the covid pandemic? If they do refuse him entry, what happens?