In theory the information from ZebOS (imish is the shell for ZebOS), should be available from TMM (F5 system).
You just need to find the correct command to get that information.
I only found the route command, but does not have any command useful for your case:
https://devcentral.f5.com/wiki/irules.route.ashx
Here is the BGP documentation:
https://support.f5.com/kb/en-us/products/big-ip_ltm/manuals/related/arm-bgp-command-reference-7-10-6.html
About your second questions, I don't think there is any iControlRest layer for imish.
iControlRest is a layer on top of tmsh, so should not work with imish commands.
About v11 or v12, that is a long conversation.
If you need a new feature in v12, just go with v12.
If you just want stability, go for 11.5.X or 11.6.X.
Read this solution as is very important if you are unsure about the version:
https://support.f5.com/csp/article/K5903