The previous previous session of 200 tabs of webpages were also created by clicking History->Restore Previous Session, and Firefox doesn't actually open all the 200 webpages when I restored it, but open each webpage when I actually click its tab, and I didn't click all of the 200 tabs. Note that it seems to me difficult to find out the previous previous 200 webpages' URLs from most recent history in Firefox. Is there some way to restore the previous previous session of 200 tabs of webpages? Now clicking History->Restore Previous Session only restore the single tab of webpage. But instead of doing that, I clicked a new tab and opened a newpage, and closed the tab, which closed Firefox out of my expectation (in Chrome browser, closing the only tab doesn't close the Chrome browser). When I started Firefox again, I had a chance to restore the previous 200 tabs of webpages, by clicking History->Restore Previous Session.
I closed Firefox, and then rebooted Ubuntu.
I opened about 200 tabs of webpages in Firefox 59.0.2 (64-bit) on Ubuntu 16.04.
