yes
Are you seeking a visitor visa for the UK?
Yes, you can apply for a Canada visitor visa from the USA.
Do you intend to apply for a family visitor visa to the UK?
Of course not. You cannot work in Singapore with a visitor's visa. This would be illegal. You have to apply for a Singapore work visa.
Depends what visa and what country
Yes, a return ticket is typically required for a US visitor visa to show that the visitor plans to leave the country before their visa expires.
Yes, Indian parents can apply for a visitor visa to the USA.
Do you have the required consulate letter for your visitor visa application?
Nobody can work in the visa on a visitor visa. Short duration courses like cookery class that will not add any credits to a course can be attended using a visitor visa. But working in the US, that will enable you to draw salary is not allowed on a visitor visa.
The maximum stay allowed for a US visitor visa is typically 6 months.
Have you provided all required documents to the consulate for the visitor visa application?
As a visitor on a visa, you can typically stay in the USA for up to six months. It is important to adhere to the terms of your visa and not overstay your allowed time.