Psychology in USA

This link has information about the scholarships available to Indian students studying in US.
https://studyabroad.shiksha.com/scholarships/usa-cp
Although please note that 100% scholarship doesn't necessarily cover other expenses like Visa and travel costs.

There is no specific requirement for that.

Hi, You can enquire or check with the colleges for scholarship opportunities. Scholarships are given mainly on merit, you will be considered at the time of application for such scholarships. You can check the details on an university website. You can also check Aga Khan Scholarships, Fullbright Scholarships, British Council Scholarships, Commonwealth Scholarships to study in the UK etc. A helpful list below to filter out the appropriate options on basis of your budget and profile:
https://studyabroad.shiksha.com/bachelors-of-humanities-in-abroad-cl1244?country=usa-uk.

Students have to pass one or more additional tests before they can be considered by most universities for admission. These range from the standardized graduate and college admission tests such as GRE, GMAT and SAT to English Language tests, such as TOEFL and IELTS. You actually have to get in touch with the university and or college that you are planning to study in and ask them their exact requirement, since it varies.