For which reason vs For that reason

I know that 'which' and 'that' open non-restrictive and restrictive clauses, respectively.
However, intuitively, it seems to me that they don't have the same functions in the phrases 'for which reason' and 'for that reason'.

Does 'for which reason' mean 'for one reason of an undefined number of reasons'.
and 'for that reason' mean 'for only this reason'.

What is the difference of 'for which' and 'for that' as used in the above examples?

Thank you