Regarding the tailplane "struts", they were a feature on all 109s up to the F model.
Up until 1941/42, Messerschmitt was the chief designer for the Bayerische Flugzuegwerke, hence the "Bf" prefix to his designs. He was eventually allowed to use his own "Me" prefix when he acquired full control over the manufacture of his designs.
Over at Focke-Wulf a similar situation arose with Kurt Tank. Initially, planes he designed retained the old Focke -Wulf "Fw" prefix but eventually his designs were alloted a "Ta" prefix - as in the Ta-152 and the Ta-183.