If I update my pheonix to 1.3 can I still run my phoenix project that was in 1.2?
Most phoenix related tasks are run by the phoenix of your project.
mix {phoenix,phx}.new
is about the only one that is run from the archive you install/update.
So it should in theory be no problem.
If you’re talking about upgrading your 1.2 app to 1.3, the answer is yes it will still run fine. 1.3 was primarily a change of the generators, which added the concept of contexts.
I think the only issue that you will have is that if you run the new generators - for example phx.gen.schema
they will layout the files a bit differently, will expect a different module layout, and will create and use context modules. Usually the generators are only really useful early in the project anyway.