Importing database from 1.51 to new install of 1.57c. Products, Customers not loading

[torvista]

Regarding the import settings, for a local Windows installation using a 163MB sql file (production database) for the import, it always times out at 5 minutes irrespective of the options chosen.
Whereas importing from the command line takes 18 seconds. I usually put the sql in the mysql/bin directory to avoid having to type paths and open the terminal in there.
Command:
mysql -uDATABASEUSER -pPASSWORD DATABASENAME <FILENAME.sql

[Foghead]

Thanks very much brittainmark. You saved my ###### on this one. Clearly I was going about the upgrade entirely wrong.
I followed your suggestions, and all is well with the upgrade. I just need to clean up a few loose ends and do some more testing.
I have not tested the payment module yet, I but it appears everything else is functioning correctly.
I will now start researching how to transfer this over to the live serve.
Thanks once again to you and all who chimed in.

[Foghead]

Just as I thought I had it licked I ran into a new issue.
I copied the updated 1.57c sales site to the live server, as it was working without issues.
Everything was fine with the admin site or the store site.
I then went to my GoDaddy account and changed the PHP version from 7.4 to PHP 8.
After that change the store front would not open. I get a (Server Error 500).
The admin is still functional.
Any ideas what causes this problem?
Thanks much. I'm so close now.

[torvista]

The debug log will tell you the location of the fault.
Compare the corresponding file in Github 1.5.7 and 1.5.8 as it will probably have already been resolved.
This is why you should be using the latest php on your local server, to get advanced warning of such things.
You should never change the production php version without testing elsewhere first, these problems will always happen as php gets more strict every time by design.

[swguy]

> I then went to my GoDaddy account and changed the PHP version from 7.4 to PHP 8.

Stick with 7.4 for now. We're still resolving issues with PHP8.

[Foghead]

After looking into the debug logs I see I have an issue with the template Professional Blue that was installed
on the 1.51 version. It appears that it may outdated. I am going to work on replacing it with a current one.
I will also stay with PHP 7.4 for now as suggested.
Once again, thanks for all the information.