I tried to load my saved world once played with 1.6.1 to 1.8.0, I then it crashed on startup.

I also added every need mod, like UniversalModCore

crash-2021-01-23_20.49.16-server.txt

You need to take a backup of your world from 1.6.1, run it with 1.7.4, and then upgrade to 1.8.0
There's a bug where 1.6.1 and earlier worlds don't upgrade safely.

Thanks for the info, I know that that risk, I know when I upgrade to 1.7.x it won't be able to downgrade anymore. So I do this locally with a backup world archive.
I will try to upgrade to 1.7.4 first tomorrow. Thanks for reply.

OK, I have to say I can't find 1.7.4 which is not listed in Curseforge. the last 1.7.x is 1.7.3
I tried upgrading to 1.7.0 then 1.7.3 it's a smooth upgrade. but when I load the save 1.8.0 the Minecraft client froze.

I think I have solved the freezing issue when upgrading from 1.7.3 to 1.8.0, but after I upgraded to 1.8.0, the texture of all stocks is broken. Don't know why.