You will need to be a runescape member to post on forums, if you are a free user you can only browse them.
Chat with our AI personalities
You cannot send a complaint directly to Jagex, you can however post it in the "Rants" section of the runescape forums if you are non-member level 250+ or if you are simply a member.
You can't you need a forum moderator to do it.
Yes there is an area in the forums for suggestions.
You need to have either a paid membership, or 5 million total experience points, to do that.
I believe it is impossible, at this time, to simply unlock your account. Going to the forums and talking to some Jagex Moderators might help, though the account just might be lost.