父母申请绿卡

My parents are in USA now and will be visiting my sister in Canada in 16 days. could you please address some of my questions:
1. should I file both I-130 and I-485 together for them before they leave or is it better for me to file them separately?
2. they are not allowed to apply for any visas (immigrant or non-immigrant)  after they leave USA and prior to the approval of their petitions if i file them together, correct?
3. are they allowed to apply for visas after they leave USA and prior to the APPROVAL of I-130? if so, immgrant or non-immigrant visas?
4. are they allowed to apply for visas after they leave USA and prior to the FILING of I-485? if so, immgrant or non-immigrant visas?
Thank you so much.

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• Reply -863211- ♂ (1248 bytes) () 04/03/2015 postreply 09:32:17