I want to ask if i can do more accounts(bitcointalk account) in one IP address?
I believe it is possible. Just try it.
Maybe you need different email addresses for registration...But why do you want more as one account? Do you want scam someone?
You need to input a unique email address during registration in order for your account to be created. However, the email address doesn't need to be valid since no confirmation email is ever sent out. You shouldn't just put in any random email address though, since if the one that you entered is already owned by someone else
then whoever owns it can also see your PMs and even initiate a password recovery to gain access to your account.
Only if you enable notifications for PMs.