While I'm not able to answer your questions one by one...
This is my understanding of how torrents operate....
Is it like FTP?
Nope... the torrent_contents aren't all packaged up in some unknown repository... the torrent is much more dynamic than that. The torrent is broken up into tiny pieces/packets and distributed de-centrally by all of the 'participants' of the torrent.
Think of it this way...
A file is broken up into 100 units.
You are interested in obtaining those 100 units..
You connect to the 'torrent' and get packet #11,#17,#1,#8... your on your way to getting the entire file some time later. Joe-User connects to the very same torrent... YOU (more accurately your torrent software) offers him the packets you have available... just in the same way YOU got those packets from 'some faceless users' who were accessing the torrent before you.
You are a downloader AND an uploader almost immediately upon accessing a torrent and that SHOULD raise big red flags since in almost all RIAA/MPAA lawsuits involve people who are 'offering unauthorized content' to others (aka uploading). This is my impression given the stories I've read... perhaps I'm way off base here. I'm not a lawyer nor do I play one....
You can stipulate how much data you send out and at what speed (every torrent downloader can/does) and if I'm not mistaken if you aren't willing to share or share at a very low level then the people sending data to u will either refuse and/or throttle your access so a 100M file will take weeks to complete.
So in short think of it like a 'fluid ftp site' in that people can and will drop off and connect to a torrent for example lets say you started downloading a torrent at 10pm and went to sleep you may have gotten the file in total by 2am now even if you quit the moment you got the last packet of the file... you've been uploading to an untold # of users in that time span and if you didn't close the torrent download until u woke up you've been sharing parts of the torrent all night.
If you are interested in accessing content that others might have a legal objection to... all I can say is this...
1 - DON'T DO IT
2 - SEE 1
Now if you feel like playing fast and loose and or live in a country where such things aren't an issue...
1 - Find ways to connect to the internet from places other than your home and/or cell phone net connections. 'Free and open hotspots' are your friend.
2 - If free/open hotspots aren't practical then look into proxy services that will protect your actual IP address (and then hope they really won't screw you to the wall when they are pressured to reveal information to authorities)
I dunno... but to me, it's just not worth the trouble.. I guess the more mature one gets and the more assets and responsibilities one takes on the more cautious they are with things that might become ... messy! Like being told to pay the RIAA hundreds of thousands of dollars for ... 24 songs you were caught sharing.
Sad thing is LOTS of torrent users don't even know/care they are sharing said content with any and all people who join in the torrent... Like that RIAA lawyer who is busy copying tons of IP addresses and tracking them down to the carrier (cable/phone company) and then to the state and town and sometimes even the exact block where they were all connecting from and IP address can and will always be traceable to the person paying the bill and getting a 'fresh ip' doesn't save you since the net provider knows that from date X to date Y you had 220.127.116.11 and then from date Y to date Z you were using 18.104.22.168.
Torrents are MOST popular by kids in college where they have roaming wifi across the campus and aren't required to sign on and/or other ways to access the net with a greater degree of perceived anonymity however even in colleges the IT group has a pretty good idea who is using what IP at any given time however since they don't bill like cable companies do they might not keep historic records as accurately as a internet provider would.