Quick question. How can I do "exactly n times" in Opus Regular Expression? Does this {n} work?
I don't think you can at the moment. Opus's regexp syntax is the original, simple version of regexps, with a handful of additions (like putting # or #n on the end to make the expression (semi-)recursive).
If you want more complex regex features you can use a rename script which then lets you use Perl, VBScript or Javascript.