Regarding to your question about changing the attribute description from a template: According to the template structure, the description could not be edited from the created elements that is based on that template, but you can create a derived template for each element that you need to have different description:
1- You need first to go to the original template and copy the attribute that you need to have different description.
2- Right click the template and select New>New Derived Template.
3- Under the attribute templates tab of the derived template , paste the attribute.
4- Remove the attribute that you have copied from the original template.
5- Add the description that you need to the attribute for a specific element .
6- Repeat Steps 3-4 for each Element that will need a different Attribute Description.
7- Check in the changes.
8- On the element that you need to change the description , right click then select Convert> Change Template and choose the new derived template created for this element.
9- Check in the changes.