Suppose i have made my first custom template using T3, what can happen after the framework upgrade (depending of upgrade features)?
Can the framework upgrade cause problem to the template view (in general)?
Backward compatibility is a feature for most of softwares.
The dev team of T3 always try the best to make backward compatible as much as possible.
Though, there are new issues and sometimes it is can not compatible because of some deprecated features or functions.
You can always update the framework. Just do BACKUP before continue.