Multiple trades and settlement in electronic trading platforms


I have been doing some reading about brokerages and what they do. One common denominator in all is that they offer a software you can use to place trades. I liked etrade and i am curious about how i would use it.

Lets say i see a trade that can make me some money real quick. Say i spot one at 20.10 that can go to 20.40 in the course of the day. So i buy at 20.10 and sell when its at 20.40

My question is, when i click sell at 20.40, do they sell instantly and money made available plus the profit i made immediately into my account?

Second question, can i use the money i earned to make other stock purchases?

So i guess, my big question is, does etrade and other brokerage software deposit the profit immediately to my account?