Does .bit domain just support tor hidden service?
Not yet. I'll web available in the next domain spec and implemented in software proxies (DNS won't be able to support that).
And how can i configure my domain .bit to redirect to "example.com" via JSON with name_update?
Redirect is not possible without a web hosting that does the redirect. I offer this service with a new domain here :
http://register.dot-bit.org/, else 1BTC/year.
Another solution is to wait for the next spec and configure alias and translate, then, if you can add yourdomain.bit to your current web hosting, you can do what you want, if you can add the .bit domain... (not allowed by a lot of web hosting)
You can already do that but putting the ip address of your web server (or ns servers) and configure your web hosting (same remark).
Does the namecoin support only ip/ip6?
Current spec supports only ipv4 in records, but using the ns record will allow you to use ipv6 (see
http://dot-bit.org/Domain_names).
How can do the redirect with JSON value?
Using ip or ns, and then configure your web hosting, if possible.