Hello!
I have Full Mesh BGP setup.
2 upstream, 2 borders, 2 route reflectors and some Service routers.. Now all routers are ROSv6 and CCRxx hardware..!

Can you tell me from experience or recommend how to update -> ROSv7. Can I update one Border at once and check that everything works ,and continue next to router reflectors etc.. Or is it better to make full clean install or swap everything over in one maintenance windows?

thanks..

There are a couple of things you need to be aware of before migrating BGP on v6 to v7. I mentioned them several times in other topics.
v6 to v7 connections are mostly no problem, except that "refresh" does not work between versions, you need to disconnect/reconnect the peer.

I'd wait a little bit for more fixes. BGP is still buggy and no fixes in 7.11, maybe in next release.

There are a couple of things you need to be aware of before migrating BGP on v6 to v7. I mentioned them several times in other topics.
v6 to v7 connections are mostly no problem, except that "refresh" does not work between versions, you need to disconnect/reconnect the peer.

I read your other posts. Lots of information. So do you think it is possible to user border1: CCR1x ROSv6 and border2: CCR2x ROSv7, and it is possible to get a functional pack?

in general as of the time of writing ... if you do NOT need any feature from v7 but rely on BGP ... stay with v6 !
a pity you could not upgrade to the new CCR devices and other ARM(64) routerboards this way.

..., except that "refresh" does not work between versions, you need to disconnect/reconnect the peer.

or:
in bgp session "stop" and "clear stopped" on that particular bgp session you want to update.

I read your other posts. Lots of information. So do you think it is possible to user border1: CCR1x ROSv6 and border2: CCR2x ROSv7, and it is possible to get a functional pack?

My experience is only with using BGP on (small and much larger) "private networks", not with Internet peering.
With the comments and restrictions I explained elsewhere, and being careful with upgrading remote routers (I have locked myself out of routers I was upgrading multiple times because of mishaps during upgrade), I have no problems that I know of in our mixed v6/v7 network.