1) If your stereo, car stereo and Yamaha stereo dock are proprietary, i.e. have dock connectors/interfaces for iPhone, you would have to acquire different equipment. There may be a few exceptions if your equipment also handles USB connections. I've seen a couple decks where you could at least charge via USB but not play back music ,etc. YMMV.
2) Correct. Samsung runs Android so does not work with iTunes/App store.
3) Yes, if there are sufficient Android apps written for your device. Look in the Android marketplace.
4) I've yet to have to deal with one personally, but they're out there. I don't feel most users need an AV program though. YMMV.
5) Not necessarily, depending on what problems you have (or don't have) with the stock handset & apps/features that come preloaded. Keep in mind that some cannot be removed since they may be part of a carrier ROM. I like to buy unlocked handsets if this ever becomes an issue. $$$.
To start out I have had an iPhone since the first one came out. I now have the 4. I am thinking of getting a GalaxyS3 but have a few questions:
1. How can I connect the phone to the much of iPhone docs I have stereo, car, Yamaha iPhone stereo doc?
2. What about My paid for Apps in iTunes? Do I just for get about those?
3. Can I still auto upload my photos to MS SkyDrive or Google Plus?
4. I keep hearing there is a virus/malware for Android, is this something to worry about? Do I need an AV program
5. Is there crapware I need to uninstall like there is when I buy a PC?