Hi,
first of all, I'm really shocked that you have such problems.
I tested the updates very extensively in many different environments and with different forms and fields...
And I've rarely heard of problems with the updates before.
Where did you get the 1.0.0 Version, you have installed on your website in the first place, from?
It's a bit sad, that you have not made screenshots or something like that from the error messages you've got.
I would really like to know what exactly went wrong and why and I would really like to help you, but on the information you provide that is not possible. To me it sounds that in truth only small thing went wrong, which would easily have been ajusted, and the installation/update of Visforms gives quite exact messages. But I think it is to late for that, as you have a already unistalled the messy update.
Is it necessary to update?
Visforms 1.0.0 is as save as Visforms 2.1.1 so from the security point of view there is no need to. Newer Versions do have more features, but if you are happy with the features of 1.0.0 (I have a notion that you are happy with them) form the feature point of view there is not need either. If you think in long term maintainance of your website and that you maybe some day want update to Joomla! 3.x and you would like to be able to just update Visforms and continue using your forms without setting up them anew, then the update is necessary at some future moment, at least when you start thinking about the update to Joomla! 3.x.
Bugfixes
This means, that this were smaller bugs in 2.1.0 which were fixed in the 2.1.1. So you do not have to face these problems.
Do you think there is any possibility for me to get a backup of that demo installation, which I could install on my local test system to try reproducing your problems?
Kind Regards,
Aicha