meaning - Third Conditionals: "If I knew..." instead of "had known..." in casual register

I know that in the following sentences "If I had known" has to be used in the place of "If I knew" to form the grammatically right sentences. What I really want be sure of is that as a native if all the 3 examples given below sound natural to you though or do you find it odd using it that way and so on? cause I've come across this to be used that way pretty often and it makes me wonder.

Please mention sequences of verb tenses in your responds too..(e.g, In the first example Subject wishes to be informed of the object's coming as s/he was on the way. looks like same time action)

1. 
   

   If I knew you were coming, I would've arrived from work earlier

   
   


2. 
   

   If I knew you would/were gonna come, I would've arrived from work earlier

   
   
   


3. 
   

   If I knew you had come, I would've arrived from work earlier