Also, had they of done research on wills and added fact based information, than this would have made a crucial impact.
Is the writing after "Also" a restritive or nonrestrictive phrase?
I think that what is after "also" is restrictive but what is after the comma is nonrestrictive. Am I right?
Restrictive: essential
non-restrictive: non-essential
The base material is "this would would have made a crucial impact", and the material before is essential (restrictive).
http://grammar.ccc.commnet.edu/grammar/clauses.htm
Here's a better way to write that sentence:
Also, if they had done research on wills and added fact-based information, then this would have made a crucial impact.
However, "this" doesn't seem to have any antecedent -- it's not clear in this particular sentence what "this" is.
Yes, you are correct. What comes after "Also" is a restrictive phrase, while what follows the comma is a nonrestrictive phrase.
A restrictive phrase, also known as an essential or defining phrase, provides essential information that is necessary to understand the meaning of the sentence. It restricts or limits the noun or noun phrase it modifies. In this case, the phrase "had they of done research on wills and added fact based information" is crucial to understanding the impact being discussed.
On the other hand, a nonrestrictive phrase, also known as a nonessential or non-defining phrase, provides additional information about the noun or noun phrase but is not necessary for the basic understanding of the sentence. It is set off by commas and can be removed from the sentence without changing the meaning significantly. In this case, the phrase "than this would have made a crucial impact" provides additional information about the impact being discussed.
So, your analysis is correct. The phrase after "Also" is restrictive, while the phrase after the comma is nonrestrictive.