LTM and GTM running different code
I have 2 pairs of LTM 1500s (1 pair per data center) with 2G of ram, and 2 GTM 1500's with 768M of ram. Both are on version 9.4.5. I got a pair of 3900s to replace the primary data center 1500s and plan on putting 10.2.2 code on them. I'm also repurposing all 1500's and upgrading them to 10.2.2 as well.
1. What is the latest version of code I can bring the GTM's up to with 768M of ram?
2. Would there be any issues with running the older code on the GTM's and 10.2.2 on the LTM's?
3. I'm configuring the 3900's now, and I want to get them ready for production. If I establish the iQuery tunnel between our production GTM's (on the older code) and the new LTM's, am I correct in saying that will upgrade the GTM's big3d agent, and I will lose communication with all established (production) LTM units, unless I upgrade them as well, or upgrade the big3d agent?
4. Generally speaking, what is the suggested best upgrade path? 6 production units- 2 primary LTM's, 1 primary GTM, 2 backup LTM's, and 1 backup GTM? Because I would like to upgrade all Big-IP's prior to bringing the 3900's into production.