Are updates the same as re-registration? I need to get back I the loop. I haven't done background work for quite awhile but I was registered with Central at one point. Do I need to attend on Tuesday and Thursdays?

You should call Central Casting to find out. you might still be registered and not need to udate!

Depends on how long ago you last updated information with Central. If it has been over 3 years, then I believe you need to do the monday-wednesday-friday visit. If it's under 3 years, then you can go to updates on Tuesday and Thursday.

6 month re-pics soubds reasonable. I've met returners who took almost 15 year liason return to N update session on a Tuesday.

Yes you really need new pictures every six months anyway if you want to work much.