Is it possible to GROUP BY multiple columns using MySQL?
Yes, but what does grouping by more two columns mean? Well, it's the same as grouping by each unique pair per row. The order you list the columns changes the way the rows are sorted.
In your example, you would write
GROUP BY fV.tier_id, f.form_template_id
Meanwhile, the code
GROUP BY f.form_template_id, fV.tier_id
would give similar results, but sorted differently.