1.“走开”means walk away or stay away,“车来了，快走”is also right 2.in this sentence ,"了" has no meaning but must be here ,like a auxiliary word.always used behind "不"“得”for example"走不了"“办得了”

1. 开 means "away" or "to show distance" here. E.g. 走开，死开，让开，弹开，滚开，两米开外 2. 动词+不了 means someone can't do something. 了（liao3）here means something is finished or completed, such as 了结, 了断, 私了, 忘不了.

来不了 can't/won't come

NO1:开means go away. NO2:了in this sentence just is a modal particle