it作形式主语，that从句和不定式作真实主语有什么区别

It is the first time that I have been here.
能否将上句that从句作真实主语改为如下用不定式作真实主语？ 
It is the first time for me to have been here.
It is the first time to have been here.
It is the first time for me to be here.
It is the first time to be here.

假如以上说法正确的话，在语感和语意上有哪些差别吗？

It/This is the first time that I have been here.
这个句子中it并不是形式主语，而是人称代词，可以改为this。that从句不是主语从句，而是定语从句，that为关系副词。
这个句型中，不能用不定式作定语。所以你的不定式的句子都是不对的。

只有先行词与不定式为逻辑主谓关系时，才能用不定式作定语。比如：
Armstrong was the first man to walk on the moon. 
= Armstrong was the first man that/who had walked on the moon.
这二个句子意思是一样的。