And yes, you need to apply for an extension before your visa expires. I assume you gave your passport to your school or agent right? Don't trust them if they say "don't worry, everything ok." A month later they'll tell you "sorry couldn't get visa" and you'll be on a month overstay.
No, 800k OR 65k per month for the last 12 months. For your initial you can only do the 800k, after a year if you've transferred in 65k a month you can use that method.