回複：綠卡回國工作， 換公民身份在即， 如何處理？

you still need to keep your PR status. You need to keep your residency and you intend to live US permenetly and you cannot stay outside country for over six month,
1. it is OK and you do not need to inform immigration because you do not stay outside country for over six month. For the address, you need to file address change form and you have to keep your residency in US.
2 no need because of short term absence
3. you need to keep you PR status. All the rule concernning maintaining PR status apply here.

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谘詢服務, 無居保持移民身份, 無居留入籍, 入籍後保持中國國籍和護照