You actually want to keep up to date on service packs in SQL < 2014 as you won't get support after awhile if you don't.
The support policy can be found here.
Generally installing Service Packs is safe but for any production system please make sure you have a strong backup model in place and hopefully a test environment to simulate all changes for ...
Very quick and easy solution would be to setup a CMS (Central Management Server)
This enables you to run queries on groups of servers.
So if you make a production group, you can run a query on all of them at the same time
Would return you all the versions of the group.
If you're managing a bunch of different servers, a CMS is always a ...
Query 1: You have to look this up in the release notes. Normally you can do that, but you always need to check the release notes regardless. There is a possibility that it is not possible. Please refer to this link, which will guide you to all the SPs and latestes CUs available, including the release notes.
Query 2: ...