How to Save Website Pages for Offline access in Firefox/...? I need to save the website of some shops etc Power.fi because you cannot use LTE data in their shops (metallic halls) but I need to compare their prices to their website prices and others. 
Options of Internet Browsers


Firefox because you can install there addons
Chrome not because you cannot install addons in Android Chrome   
...


Options of the goals


It would be nice to save daily catalogs of the websites (whole website). 
And then when time is in need, just take pages which you need (just a page). (Akhil's answer proposal here)
How to Store 777 single pages to one frontend/client/...?


Firefox plugins under test


ScrapBook - does not work in Android Firefox because I cannot even install the app in Android; pressing install just goes infinitely but never installs; restoring the page shows that nothing is installed; I did restart the browser but no difference. 
...


Chrome (I really would like to find a solution for this as soon as possible Google allows the addons)


...


Phone: Oneplus 2
OS: CyanogenMod 13
You can try HTTrack Website Copier. Seems to match your needs fully, not tried by me :

HTTrack is a free software (GPL) offline browser utility, allowing you to download (copy) a website from the Internet to a local directory, building recursively all directories, getting html, images, and other files from the server to your device.
HTTrack arranges the original site's relative link-structure. Simply open a page of the &quot;mirrored&quot; website in your browser, and you can browse the site from link to link, as if you were viewing it online.

Edit Tested it now

All sites do not permit copying - this site doesn't:). For reasons see FAQ

Can be very time consuming when on WiFi. I tried on Amazon India and aborted after 7 minutes . It copied the first page fully, it looks like, but you can set up rules

I tried on a smaller banking website and it was able to copy fully with three levels of linking


You have to test and see if it works for your sites
Refer comment. Copied the content of LG TV as shown below. Note the download link location in internal storage and the third one shows internal link opened up. Took one minute