Hi Anhvu,
There are some old Chrome version on FileHippo: http://filehippo.com/download_google_chrome/history/10/
However, TestComplete 11.20 officially supports Chrome 46. If you face any issues, please submit them to our Support Team. Our R&D team will fix it and you will continue using the up to date browser version.
I currently have some issues with multiple Chrome browsers and TC11.20 (I have workarounds in place now but behaviour is not the same as it was with NPAPI - but only with multiple browsers open), but other than that, it works just fine with it, as Tanya says.
I gave up trying to hold it back on an NPAPI version. Too much hassle constantly trying (and failing) to stop it auto updating, and then constantly un-installing and re-installing when it did.
You'd be better figuring out why the current versions don't work. You'll need to update at some point.
