Opponent plays promising future, and reveals flurry of blades, can i play riposte from mmy promising future carad

No — not with the opponent controlling Promising Future. Since they're the caster, you're the "next player," so you play your chosen card first: your Riposte is appended to the chain first, finalizes first, and sits below Flurry of Blades. Flurry is played second, so it's the newest chain item and resolves first (LIFO, Rule 340.1). By the time Riposte resolves there's no spell left on the chain, so the counter — and the +M from it — does nothing.

Targeting isn't the issue: pending items are already on the chain (Rule 329.1), so Flurry is a legal spell choice. The problem is purely the order — your spell resolves after theirs, so it arrives too late.

The mirror case works: if you controlled Promising Future, the opponent plays first and your Riposte finalizes on top, resolving before their Flurry — that's the Windwall/Promising Future ruling (FAQ #5947). Also note Riposte still costs its 2 power even though Promising Future ignores energy costs.