Do you think gay cure therapy should be illegal? Or should gay people be allowed to have it if they want it?

It certainly should be legal for people who want it. I also don't think it should be illegal for parents to at least encourage their children to be straight.

If it's entered into voluntarily, no, I don't think it should be illegal. I don't think conversion therapy works and I think it's harmful for the people who undergo it, but I think adults should have the freedom to choose whatever treatments they want. Children would be a different issue however.

But doesn’t it come under false advertising, and false advertising is illegal is it not.

Physics, ghost hunters and crystal healers are allowed to operate, and those don't work either. What qualifies as "false advertising" is very strict legally, and usually refers to things like deceptive packaging, not religious or pseudo-supernatural practices that people believe in of their own volition.

What do these therapies consist of? The only shocking example I've heard of is gangbanging the gay out. Is it usually something like talking or group therapy?