Upgrading Drupal

I have a site running Drupal 5.21 that is updated very, very rarely. It's essentially an archive of photos, videos and audio, and occasionally there are new blog posts. I'd love it if I could have commenting but don't know how to achieve that without getting an avalanche of spam. (I'm running Text captcha 5.x-3.1 but it doesn't seem to help.)

I just started creating a new drupal site. Instead of downloading all of the necessary contributed modules, I copied them from a different test site I had made recently. There were a few modules which needed to be updated, so I put the site in maintence mode, deleted those module folders, pasted in the new ones, ran the update script and now I have no errors. However, now it still says "Operating in Maintenance mode - Go Online", and clicking "Go Online" brings me back to the maintenace configuration page, but I remain in Maintenance Mode! I cleared all caches and nothing helped!

I have a Drupal 6 site - example.com

Is it possible to install Drupal 7 on a subdomain - subdomain.example.com - for the purpose of migrating the site in parts?

So I decided to run some neglected updates today (animaltree.org is the site), and when running the security update for views I killed the site. I attempted to fix the problem through drush rr and I did get a bit further but I am now stuck. I can't clear the cache, specifically the menu cache, without running into this error:

Fatal error: Class 'EntityDefaultMetadataController' not found in path_to_drupal/sites/all/modules/field_collection/field_collection.info.inc on line 8

I have a Drupal website that's been sitting in mothballs for the last 4 years. When I go to the Drupal Available updates page, there's about 30 or 40 updates total listed there that show they need to be made.

I have a Drupal 6 site with Views 2. When I upgrade to Drupal 7 and Views to version 3 some of the fields stop working, for instance imagefield. Before upgrading Views module I've upgraded the fields with content migrate. Is there any way to migrate the old D6 fields to D7 in the views?