I have put dragons to upgrade to level 3 in the laboratory. Is it possible to train dragons during this time?
Yes, you can train a unit even if it is currently upgrading in the laboratory.
Once the unit is upgraded in the lab, ALL of those unit will become the new level.
Yes, you can train the unit even if it is upgrading. When the dragons are done upgrading, all the dragons in your army camp and barracks training will level up.
To actually answer your question, yes.Even as a unit is upgrading, you have the authorization to train in your barracks. However, until the upgrade is complete you will only have the current troop level.Once the upgrade is complete,you have your troop upgraded and you will be able to use it at that level.