ArduPilot 2.6 and newest mission planner

Loaded new MP, followed wizard, flew kinda ok. moved stuff around and mounted, wanted to recalibrate everything. now, after a firmware load (does this everytime. tells me board is retired) loads firmware fine, but never connects again unless i load an older firmware. then, nothing else works. it will connect to MP, but no GPS, no calibration etc. and now my radio telem will not connect except for the initial load settings. getting bored with this.

I also have a related question. News says new firmware no longer fits on apm 2.6. So if I buy a new apm 2.6 and connect to mission planner for first time set up, it tries to install latest firmware. Will mission planner automatically only try to install the last firmware that fits or do I have to work around this somehow