Keep lvl. 1-5 buildings

Hi everyone, is there a way to keep buildings at any lvl. from 1 to 5 without the annoying upgrade message popping up? I want to build a city with variety of buildings not just luxurious lvl. 6 which all look the same. 

Second, can EA please give us railway bridges permanently? I think it’s such a necessary item to build a city with rivers and railways. I have a river with a railroad going across it, so i basically have a gap in the river with the railroad being on the ground which looks awful, but there is no other way.