You can't, sorry.
Chat with our AI personalities
Nope :P
I believe you can, even at the same time, but if you do a message pops up saying that you're logged in from another location. You can't, however, have 2 accounts playing on the one server.
no if online yes if offline
The only way to have to RuneScape accounts without making a new e-mail is to already have two accounts and then register only ONE of them. You cannot have two accounts now unless you have multiple e-mail addresses also. If you have multiple e-mails, then you can just make two or more accounts and register each with a different e-mail. However, if Jagex finds out, then the accounts known may be banned forever.
You can, but they can't be on the same server. The first person that got on the server will be kicked, the second person will instead be on.