Okay messed up early and converted a farm to a barracks. Have upgraded barracks to level two if I convert back to farm then convert forge to a barracks will I lose the upgrade
No - both buildings retain their level
You can never destroy or downgrade any building
or build more of any building than permissable - the castle builder aspect of the game is essentially fool-proof
iBut you are going to want that farm more as a farm than as a barracks. convert a forge to barracks and chalk the one level into the farm/barracks as a learning cost.
Okay did the switch and did not lose the upgrade. Did not want to pay for that upgrade again thanks