Stronger passwords and security questions

and a module to prevent users from changing other users' password using the "forgot password"?

A user cannot change (that is, reset) another user's password. What is sent in the email is a link to a temporary login. The password isn't changed.

[...] strength of the chosen password
[...] and ask for security question(s).

By adding all these nuisances you're forcing your users to write down their password. You're compromising their security. I'd also say that you're harassing your users.