This is the place where I was born.
I don't know the time when I was born.
I know the reason why she is angry.
I know know how he seduce her.
Can the above sentences changed into the below?
This is the place that I was born.
I don't know the time that I was born.
I know the reason that she is angry.
I know the way that he seduced her.
or... do I have to add prepositions at the end of each sentences? like...
This is the place that I was born in.
I don't know the time that I was born in.
I know the reason that she is angry for.
I know the way that he seduced her in.
None of my grammar books give me clear answers. Pleas help. ㅠㅠ
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.
Thank you guys!! ^_^
 This is the place where I was born.
into (structurally dubious)
 ?This is the place that I was born.
you are substituting one relative adverb (that) for another (where).
When you then transform  into
 This is the place that I was born in.
(notwithstanding the unnaturalness of , as others have pointed out) you are substituting a combination of relative pronoun (that) plus preposition for the relative adverb.
Although generally speaking, in this kind of expression (i.e. concerning a place in, on or at which something occurs), construction  will tend always to be acceptable, there are fairly strict limitations on the usability of  and .
While  will often, as here, be considered unidiomatic or inelegant,  may in many cases be completely unacceptable.
For instance, although we can say
This is the school where I went.
This is the house where I lived.
This is the school that I went to.
This is the house that I lived in.
we cannot say
*This is the school that I went.
*This is the house that I lived.
In view of such complex syntactic and idiomatic restrictions, my advice to the unsure learner would be to avoid the use of relative adverbs altogether and stick to the somewhat formal but relatively "safe" [preposition + whom/which] construction (the house in which I lived, the school to which I went, etc.)