Support Forum

1, 2, and 3 are all core SP options.

4 is available in V4 via program hooks but is more easily accomplished in V5 currently in beta.

5 is built in using the rpx/janrain service. You can see that working on our site here.

6 is NOT an SP function. Remember that SP is a plugin to WP. Users register within WP and access the forum via WP. There are plugins available for WP that should help with this.

7 I have never used it myself but we have users using NextGen successfully. SP does optionally support the use of Wp shortcodes.

8 probably depends on the plugin being used. In theory, if the plugin being used is well behaved then it should be fine and I believe we do have users doing this. There are one or two that I know cause problems because they are too geared towards blog posts. It would actually make an excellent SP V5 plugin project for someone.

we do have an importer that should (note the should!) import forums, topics, posts and users from SMF. The majority have been successful with it. It currently only works with V4 as we have not yet updated to to V5 but hopefully will be

No sorry - it is our importer 'engine' that requires updating so this effects all source systems.
I do hope to find time to do this in the next couple of weeks. The V4 system is available however.