When an individual has/have [?] a unique idea (...), it is said that they have (...)

[Conatus]

Hi teachers and colleagues!

I've just de-recorded this phrase out of a podcast audio file:

"When an individual have a unique idea or arise at a unique solution to a problem, it is said that they have thought 'out of the box'”.

Then I looked up for "an individual has" vs. "an individual have" at Google Book Ngram:

Google Ngram Viewer

And I've notice that there are millions of results to "an individual have" on Google Search:

https://www.google.com.br/#q="an+individual+have"

In the above phrase, is the verb conjugated in the 3rd. person plural form -- although "individual" is necessarily just one person -- for a question of parallelism with "they" used in place of "he or she"?

If so, I'd be wondering/I'd wonder [?] whether one could make the same phrase in the following form:

"When an individual has a unique idea or arises at a unique solution to a problem, it is said that he or she has thought 'out of the box'”.

 

[5jj]

"When an individual have a unique idea or arise at a unique solution to a problem, it is said that they have thought 'out of the box'”.

That is not correct. 'Have' needs to be 'has'. 'Arise' needs to be 'arrives'.

Then I looked up for "an individual has" vs. "an individual have" at Google Book Ngram: Google Ngram Viewer

And I've notice that there are millions of results to "an individual have" on Google Search:

Most of these involve an auxiliary: Can/does/will/etc an individual have ...

 

[Tdol]

If so, I'd be wondering/I'd wonder [?] whether one could make the same phrase in the following form:

"When an individual has a unique idea or arises at a unique solution to a problem, it is said that he or she has thought 'out of the box'”.

Yes, if you change arises to arrives.