Aloha Tatiana! I wish your questions had straightforward easy answers – and if you are government funded it kind of is. (See here: https://www.ada.gov/websites2_prnt.pdf) if you are not government funded, this is something that is currently being debated in the legal system. That being said, the WCAG 2.0 guidelines are a good set of guidelines to help protect yourself if you feel you should. (You can see more on WCAG here: https://www.yokoco.com/find-out-how-to-make-your-website-compliant/)
This title prohibits private places of public accommodation from discriminating against individuals with disabilities. Examples of public accommodations include privately-owned, leased or operated facilities like hotels, restaurants, retail merchants, doctor’s offices, golf courses, private schools, day care centers, health clubs, sports stadiums, movie theaters, and so on. This title sets the minimum standards for accessibility for alterations and new construction of facilities. It also requires public accommodations to remove barriers in existing buildings where it is easy to do so without much difficulty or expense. This title directs businesses to make "reasonable modifications" to their usual ways of doing things when serving people with disabilities. It also requires that they take steps necessary to communicate effectively with customers with vision, hearing, and speech disabilities. This title is regulated and enforced by the U.S. Department of Justice.
Most recently, however, pizza chain Domino's has been brought under suit for their website not being accessible for specialty ordering. The U.S. Supreme Court refused to review the case, instead upholding the decision of the 9th U.S. Circuit Court of Appeals who said the “alleged inaccessibility of Domino’s website and app impedes access to the goods and services of its physical pizza franchises—which are places of public accommodation.”