Hello,I am seeking a 2-year extension for a green card holder to remain outside of the US. I have a couple of questions: 1. If, for any reason, the person wishes to return to the US within the 2 years, is it still possible? 2. What are the drawbacks of being outside the US for 2 years, aside from delays in obtaining citizenship? 3. Can they still continue with Medi-Cal, or does it need to end and require reapplication upon returning to the US?

Any insight would be greatly appreciated.

1) Yes absolutely. They would present their Green Card and Travel Permit (small green passport-esque book) to the agent. No issue at all.
2) No drawbacks apart from citizenship delay.
3) can't help here, sorry,

From earlier posts you asked a similar question in 2024 regarding your parents who got their green cards in 2023 and then left the US.
So they have never returned?
With regard Medi-Cal this is the low income health insurance for California residents (equivalent to Medicaid). Unless they have continued to pay into Medi-Cal would have thought they would need to re-apply for it.

One thing to add, my understanding is the Travel Permit must be applied for, approved and received before the GCH leaves the US.

This is incorrect. They can leave the US while the Re-entry Permit is pending. (Though they do have to be in the US to do the biometrics, if it is requested.) In fact, on the I-131 form itself, there is a question asking whether they want to pick up the Re-entry Permit at a US consulate abroad after it is approved.

You might be thinking about Advance Parole, which is a completely different thing.

Yep, you're right, my bad. I was indeed thinking of AP. Sorry!

California medical plans can be confusing. You describe what is called Covered California. Medi-Cal includes Federal Medicaid, but is broader in its scope and availability. OP may want to talk to the DPSS people.

BTW, OP’s questions do raise further questions and has me reacting “Danger, Will Robinson.” Consultation with immigration counsel who has tried an abandonment case might very well be in order.

Furthermore, deponent sayeth not.

They returned and have been living here. They are looking to go back for longer period of time so looking for different options.

MediCal only provides coverage in California and is restricted to Californian residents. If your parents are leaving the US for an extended period they would no longer be eligible for MediCal because they would no longer be California residents.