It depends on the template. If it were to have families, or some other non free feature then it won't work if all you have is the free version.
Each template has its own comments section, you might ask the individual template creator if it is compatible.
Obviously you would still not be able to generate revenue with the templates till you have a full license.
Not entirely true.
The free version can open and run projects that have used non free features, and also if over 100 events. The free version just cannot alter the project in any way.
So the OP could purchase a template, as perhaps a learning tool, but if they wouldn't be able to amend it if, as you say, it overstepped the free version parameters.