Create A Forum - Support Forums

First of all, I am sorry if I have posted on the wrong board.
I am totally new in forum related stuff. I have created a forum with createaforum and linked it up with my domain. Now that I am planning of investing on it for fulfilling my goal. Anyway, some questions arised here-

1. How much secure my forum is? Possibility of being hacked is related to mainly what?
2. Assume hacker got access of my forum, how can I get it back?
3. How to back up my forum so that even if something unexpected happen, I will be able to get back all of the members back.
4. Can I keep the hosting system out of my forum so that I don't need to purchase any hosting plan. If I want to use the by default forum option, is there any limit how much member can be registered? I mean is it must to purchase a hosting plan for a big community?

Thank you. Don't laugh at my noob question. Everyone was noob for a while.

1. As secure as you make it. The main issue is do not give people admin level permissions and you are safe. And use passwords that are not used by other sites.

Thank you. Got it.

2. We have the FIXCP system you are sent a login on signup which gives a password sent only once. Which allows to restore admin and clear bans.

Where have you given the password? I didn't receive it.

3. We backup forums. But if you want an SQL level backup a one time fee for $50

I want to back up so that I don't have to lose my member registration. Is it available for free or SQL back up is required?

4. Yeah, we specialize in just giving forum level access. No limits on number of members, topics, posts

I think there's limit on avatar's and attachment. What if someone uses third party hosting and just embed here with code? Does that require me more space?

3. No only way is paid backup.

Can I do it later? For example, for now,my forum is new. No one will attack it. So, I am thinking of having back up after couple of months. Will it be a problem?
Is the cost $50 onee time?