I was in US from Jan 1, 2019 to Aug 11, 2019 and moved to (Ontario, Canada on Aug 12. 2019. I have received the W2. Am I eligible for foreign tax credit, OTB, GST/HST

For the foreign tax credit, yes, you might be eligible depending on what amounts you paid to the US government.

 

For the other two credits, residency is only one part of the eligibility criteria, so I can’t say if you are eligible or not.

 

This Government of Ontario page shows the eligibility requirements for the different part of the Ontario Trillium Benefit: https://www.ontario.ca/page/ontario-trillium-benefit

 

This CRA page shows the eligibility requirements for the GST/HST Credit: https://www.canada.ca/en/revenue-agency/services/child-family-benefits/gsthstc-eligibility.html