I need to my 2021 W-2 as soon as possible to prove I worked this year but that file is not available yet. What can I do?

whoa - slow down....

2021 w-2's will not be available until January 2022. 

you cannot 'apply' for the 3rd stimulus.  The IRS will send it to you  (based on prior tax filings) or you can obtain it from your 2021 tax return when you fill that out early in 2022.  You can't 'apply' for the 3rd stimulus. 

If you are an international student, do you meet the qualifications? do you have a Green Card?

what Turbo tax link are you referring to????

Eligibility

Most eligible people won’t need to take additional action to get a third payment.

Due to new income limitations, some individuals won't be eligible for the third payment even if they received a first or second Economic Impact Payment or claimed a 2020 Recovery Rebate Credit.

Generally, someone is eligible for the full amount of the third Economic Impact Payment if they:

• are a U.S. citizen or U.S. resident alien (and their spouse if filing a joint return), and
• are not a dependent of another taxpayer and
• their adjusted gross income (AGI) is not more than:
  • $150,000 if married and filing a joint return or if filing as a qualifying widow or widower
  • $112,500 if filing as head of household or
  • $75,000 for eligible individuals using any other filing status

Payments will be phased out – or reduced -- above those AGI amounts. This means people will not receive a payment if their AGI is at least:

• $160,000 if married and filing a joint return or if filing as a qualifying widow or widower
• $120,000 if filing as head of household
• $80,000 for eligible individuals using any other filing status