1.would you have come to his help,had you been free?正常语序是if you had been free,would you have come to his help?显然这是对已发生过的、过去的事情的假设
所以答句中用一般过去式 i was ,非虚拟语气
2.该句相当于if you prepare for the worst in advance,you will not feel too sad if you fail.主句将来式,if 从句一般现在式,故选prepare原形