Diễn đàn hỗ trợ Firefox

I have three devices, a desk top, a laptop and an iPad. The desktop is running a very outdated version of Firefox which means it is not compatable just to update it. The forum tried to help me with this a while back, but it was deemed not to be possible, and the best way would have been to do a fresh new install, but there was noway to save log-ins/passwords bookmarks. My devices all have the Firefox sync and that is so far working well. My question is, if I dragged my PC's Firefox into the present by performing a fresh new install, would my synced items install ok....after invoking the Sync feature on the new install. Logic tells me this should be so, as it worked ok with the new iPad, but I know from experience that logic doesn't always come into play. (Windows7) Many thanks

Tried ticking the box in preferences

Tried the about:config

changed it to 2 and it is still not working on my new macbook pro

version 10.15.7

macOS Catalina

I was having trouble with Firefox not loading pages. I upgraded from v57.0b9 to the latest one (out of desperation), which didn't help. I've now reinstalled v57.0b9 but can't sign in in order to sync. Any ideas?

Attached is the message I get when trying to sign in.

Can I pull up my bookmarks saved on my laptop on other devices that has Mozilla. I updated my Browser on my PC and when I did I lost all my bookmarks. I have not updated the Browser on my laptop and I am beginning to have connection problems and I CANNOT lose my bookmarks.