向 and 对 mean the same thing in this sentence.And I can't come up with any situation in which they aren't interchangeable.So I guess they are.(love to know if I am wrong about this). 向 and 对 mean TO. 和 and 同 mean AND。 But I don't think 给 would be the proper answer. Pls point out any mistake I made or discuss any question with me. Hope my answer will help you.

except 和、同、给，others can.（最符合语法） 向，对：to， 向前：to a direction of your facing. 向后：to a deirection of your backing on 和、同、给： when you express to talk with sb, it's ok. chinese like this： 我同你说，我和你说，我同你讲，我和你讲， 我给你说(个事)，你给我说(清楚) 【Chinglish：i give you talk a thing. you give me talk clearly. how to understand 给 in here? try to imagine a situation：you pull his a corner of a garment, and you talk sth with him . do you see？ when you pull his garment, he just like give himself to you. 你给我说（清楚）is the same as the imagination: you pull his garment or arms, because you do not allow him to leave. you are angry,so you pull .... when you pull , he just like give himeself to you.】， = 我对你说（chinglish: i face you said.what i face？ i face you , and what i face you to do？i face you said 对 is 面对的简化形式，省略了面（face），因此意思更像 like to（我可以是侧对着他说，等等） ，面对更强调face to face） 你给我过来（给in here：you take yourself to face me！= you come here immediately！（imagine: he is far away from you, you can't catch him）） 工人和/同经理表达感恩 : it is not very accurate in here. two sorts of translation below. the worker and the management , express gratitude.sould like no subject.(*) but, the worker express gratitude with the management.(√) so, native speaker can understand. 工人给经理表达感恩， 错误！ 这里想表达的意思是：工人表达感恩，对经理。 accoding to i said above 工人给经理表达 subject变成了经理。 你给我过来，subject is me。because，i pull your garment to say。 而且，很少这样说，no i pull your garment and express......

工人.向..经理表达感恩（的心情）。 工人对经理表示感谢

工人...经理表达感恩。 工人向經理表達感恩=工人對經理表達感恩.The same meanting.

向 and 对 is NOT always interchangeable. 比如，“向”还可以表示“朝”某个方向，“对”不可以。eg. 我向他走去/ 他以最快的速度跑向终点