It doesn't mean that the same can be done next time just because it worked previously.
It doesn't mean that the same instruction will be executed just because it worked before.
This instruction worked before, but it doesn't mean that it always does.
Programの instruction がexecutedされたからと言って、..という訳ではない、という文章は、
It doesn't mean that .... just because.....
と言うように表せます。
前回動いた、は、"it worked previously", "it worked before"などと言います。
「正しく実行されるとは限らない」は、
"It doesn't mean that the same instruction will be executed correctly"
「同じように実行されるとは限らない」は、
"It doesn't mean that the instruction will be executed in the same way."
「いつもそうなる（正しく実行される）とは限らない」
"it doesn't mean that it always does."
日本 
