the visa fee? 1000 Baht for a Single Entry Tourist Visa.

If you apply for the visa, you must pick it up the next day. Otherwise they will void the visa.

Correct. And before the 25 of July you can take the paperwork to immigration to get an extension of stay.

You have another stamp in your passport, that shows you when your current stay expires. It looks like in the picture. Until that date you either have to leave the country or apply for an extension.

As far as I know, Russians are permitted to stay up to 30 days (Bilateral Agreement).

When you cross the border they will stamp you in for 90 days. After that you will have to get extensions of stay at your immigration. You will need the paperwork from your school.

I'm at a Thai school in Bangkok and got my visa in January. When I crossed the border I got a 90 days stamp. Before that one expired I took the paperwork from school to immigration and got an extension of stay by 60 days for 1900 Baht. Before my current stamp expires I will again have to go to immigration to apply for an extension of stay.

I would not recommend to post all the personal details (name, passport number, ...) online.

Don't worry. You will make it. I took the Nok Air flight and landed at 7am, so one hour earlier. I arrived at the consulate at 9am. You will be fine.

Yes, only morning, I think until 11.30am.

I arrived at the consulate at 9am and got number 472. I booked my return flight in advance at I think 9pm so even if I was the last one collecting my passport, I could have made it.