1. How do I claim the US-China treaty as a resident alien using TurboTax premier Mac? 2. How to recover the treaty credits from previous years as I forgot to claim them?

TurboTax does not support Form 8833 Treaty-Based Return Position Disclosure Under Section 6114 or 7701(b) . 

You can prepare Form 1040 using TurboTax and print and prepare your Form 8833 separately to attach and mail.

You can amend your 2019, and 2018 returns.  Your 2017 return can be amended - it must be received by the IRS no later that April 15 2021. 

2018 and 2019 can be amended until 3 years from the original due date of their returns - April 15, 2022 and July 15, 2023.  Treaty-Based Return Position Disclosure

How do I enter the tax treaty amount in TurboTax though? Is it $-5000 under Less Common Income/Miscellaneous Income, 1099-A, 1099-C? So I'll have to print out the forms prepared from TurboTax and attach form 8833 and mail the return to the place listed on 1040?

Yes, it is entered as a negative amount to Other Income, as you mention. You do need to attach form 8833 and mail your return.

Here is the menu tabs you use to enter the adjustment:

1. Federal
2. Income and expenses
3. Less common income
4. Miscellaneous income
5. Other reportable income

Enter a description for the entry (treaty abbreviation)  and the amount as a negative number.

Thank you! How do I get all the forms I need to mail to IRS from TurboTax desktop (Mac)? Where should I mail them to? Can you provide some instructions?

How do I amend for 2017-2019 tax returns to recover the US-China Treaty? Do I just attach three 8833 forms from 3 different years?

No, you must prepare a Form 1040X for each year to claim the $5,000 income exclusion under the US-China Tax Treaty. 

Complete each Form 1040X with the explanation "Amended to claim Income Exclusion under US-China Treaty Exemption" 

You then need to complete and attach Form 8833 to each Form 1040X and submit to the IRS.  

I'm claiming educational credits (e.g., American Opportunity Credit) using 1098-T from my school as a resident alien for tax purposes. Can I still claim the US/China Tax Treaty? Is only one of them can be claimed?

I believe what you are asking is can you exclude income under the US/China tax treaty and also claim an education credit. 

You can, but your education credit may be limited if your income is reduced by the treaty. Depending on what education credit you qualify for, some or all of it may be limited to the amount of your income tax. So, if you reduce your income you may also be reducing the allowable education credit.