make a trigger that runs after 600 seconds have gone
then make an Integer variable and set it in the trigger to (Random number between 1 and 4)
lastly, check with "If - Then - Else" actions if, for example, the Integer variable is 1 set the level of Iron Forged Sword for the player to 1(or Level of Iron Forged Sword for the player + 1 if he can research it for himself), until you have one "If - Then - Else" for each of the upgrades