AD Forest Level Upgrade Procedure 2003>2012R2

We are in the process of upgrading our single domain forest from 2003 to 2012R2. We have several site- (On=On-Prem and AWS)

Currently we have all 2008 Domain Controllers in a 2003 Forest Level. We ran Forest Prep already.  Once forest level is raised I will run DCDiag to make sure all looks good.

Questions-
Once on 2008 Forest level, can I promote a 2012R2 server to Domain Controller?
Once on the DC role is on a 2012KR2, can the forest level be upgraded to 2012R2 from 2008?
Is there any Forest preps that needs to be done in between?
Any one know of any "Gotcha" during this process?
GGHCAsked:
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Cliff GaliherCommented:
You can add 2012 R2 domain controllers. It will do any schema updates when it is promoted. So yes the ad prep /forestprep gets run, but on 2013 it is no longer a manual step. But since it is a schema change, backups should still be made first.

Your forest and domain functional levels can only be as high as the LOWEST version DC. So in your scenario you could not raise the functional level to 2012. Not using less and until you retire the 2008 DCs.
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RobertSystem AdminCommented:
Yes you join a 2012 R2 server to the domain and make it a DC even when the functional level is 2003.
You just cant raise the functional level to 2012 if you still have domain controllers running at a lower level.

So if you still have 2008 DC's don't raise the functional level to 2012.

If you have not already done so I would recommend reading this article.
https://blogs.technet.microsoft.com/askds/2011/06/14/what-is-the-impact-of-upgrading-the-domain-or-forest-functional-level/
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GGHCAuthor Commented:
Thank you for quickly answering my concerns and providing guidance!
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