Yes, at the opening screen of the DVD620, select setup, then at the next screen select "Display". You will see two 4:3 choices at the top . Just check the box that looks best on your set. Hope that helps.
I don't know. I have used it frequently, but all of the DVD's I played on it were the new 16:9 aspect ratio, and that is what my new LG TV handles well. HOWEVER, I expect that your Blu-Ray player will play the 4:3 ratio. Just check your manual for instructions.. Usually the players automatically sense the format of the disc it is playing. I do know that it plays older DVD's [not only Blu-ray]. Thus, it must be able to adjust the format to 4:3 when necessary.