What are the things needed for my friend in US to sponsor me to continue my college in US?

See https://www.uscis.gov/ https://www.state.gov/

What document does a bank need to transfer control of retirement/investment accounts?

Washington State law has adopted the Uniform Power of Attorney Act at RCW 11.125. https://app.leg.wa.gov/RCW/default.aspx?cite=11.125. ...

You might want to talk with some attorneys about suing and asking for various types of relief from the courts (i.e. injunction, declaratory...

What happens if a husband refuses to produce his wife's will. divides her assets to people that are not named as the beneficiary

You should retain an attorney and start a probate action, especially if your mother had separate property. See...

The appropriate governmental personnel ought to be able to communicate enough to address the issues.

Can a guest turn off my water in a rental?

Landlords of residential premises have a duty to provide premises fit for human habitation. RCW 59.18. https://tenantsunion.org/en

Questioned by cops minor child?

911 calls can require reasonable police investigation. See...

See https://www.equalrights.org/legal-help/know-your-rights/sexual-harassment-at-school/

Fraudulent charges

If you are the victim of a crime, you can call the police. You can sue to get your money back.

Can I return a used car to dealership as-is if transmission slips or engine problems?

See http://www.atg.wa.gov/used-car-considerations