Can I just upgrade to 3.0?

Help for v2
#1

Can I just upgrade from 3.x or do I have to install 2.x first?

And why can’t I post to the v3 help forum?

#2

Yes, you’ll have to uninstall any previous version of Comodo Firewall Pro before upgrading to V3.

Cheers,
Ragwing

#3

Do I need to delete some temp after uninstalling? Will my uninstalling process remove my “allow/disable” program config file ?

#4

No, the temporary files won’t interference with the installation of CFP 3, but you can delete them safely.

Yes, uninstalling CFP 2.4 will also delete the configuration file.
If you want to, you can try this script to backup CFP 2.4’s configuration:
https://forums.comodo.com/help_for_v2/script_to_backup_cpf_v24_firewall_settings-t2366.0.html

Cheers,
Ragwing