Yes, you can. Wireless connection is not different from wired connection in a sense of functionality.
yes or you could link to another persons
yes.
There are a few ways of preventing easy and casual connections to your computer by non-authorized people. The first is to place a password on every account on the computer. A second is to enable the OS firewall on the computer. Since this question was placed in the Windows XP category (among others) we are talking about Windows OS. XP - and Vista and Windows 7 all have built-in firewalls that can be enabled by users. Another way of preventing the easy connection by unauthorized people is to shut down your computer whenever you are not using it. Installing a good antivirus/antispyware/antimalware program on your computer will also significantly reduce the risk of having malware installed on your computer that will open up security holes that would make easy connection to your computer possible. If you have a wireless router, you should enable security on it. There are many other ways to protect your computer, but if you do the ones already mentioned, you will have at least taken your computer out of the category of susceptible to "easy and casual connection" for unauthorized persons.
"The police are searching for three persons of interest in connection with the robbery."
No as long as when you go to court you got the proof that they tried to hack your computer first
yes, but you have to authenticate or something like that by entering the persons account info.
Computer access allows a user to have access to another persons computer to assist with technical problems. This is a process usually done remotely and it is done by a technician.
yes because you can burn a CD and you can cut or copy paste to the CD and insert it to another persons computer and your will be there
opening an email attachment downloading stuff from the internet
mind-body connection
You cannot see another persons friends if their profile is private.
yes