Most easy option is to apply for the Non Immigrant B visa before you make your way into Thailand.
Your employer must meet the requirements to convert your Visa Exempt Entry or Tourist visa into a Non Immigrant B visa, you have to discuss that with employer and Immigration.
No, as asked the home owner details. Or you are the home owner or you use the details from the home owner. The app is designed for home owners and fits one adress. It is not an app for tourist to use when travel around.
Open your passport, look at the stamp Extension of Stay is permitted up to xx/xx/xx The xx stand for a date and that date is your last day of allowed stay inside Thailand.