The Wizard Feat "Counterspell" states that one must Expend/ Lose your Spell slot as if you had cast the Triggering a Spell Slot. Can you Counter Spell with a Cantrip? Cantrips are not lost when Cast. I assume that you can use Cantrips to Counter other Cantrips.
But if this is True then with "CLEVER COUNTERSPELL" you can use Cantrips to counter all spells. Example is that Ray of Frost or any Evocation heightened to 5th level can Counter a Fireball Spell Heightened to 5th level with a good roll. (all you would need is a 12 on your Counteract Check if you were Identical to the other caster.
COUNTERSPELL [REACTION]
When a foe Casts a Spell and you can see its manifestations, you can use your own magic to disrupt it. You expend a prepared spell to counter the triggering creature’s casting of that same spell. You lose your spell slot as if you had cast the triggering spell. You then attempt to counteract the triggering spell.
CLEVER COUNTERSPELL
You creatively apply your prepared spells to Counterspell a much wider variety of your opponents’ magic. Instead of being able to counter a foe’s spell with Counterspell only if you have that same spell prepared, you can use Counterspell as long as you have the spell the foe is casting in your spellbook. When you use Counterspell in this way, the prepared spell you expend must share a trait other than its tradition with the triggering spell. At the GM’s discretion, you can instead use a spell that has an opposing trait or that otherwise logically would counter the triggering spell (such as using a cold or water spell to counter fireball or using remove fear to counter a fear spell).
Regardless of what spell you expend, you take a –2 penalty to your counteract check, though the GM can waive this penalty if the expended spell is especially appropriate.