• giriśam — Lord Śiva, Lord of the mountain
  Repeats the giri-epithet from v.13 — the chapter is interlocking. The Lord-of-the-mountain who will soon flee to the limits of the directions (v.24).
• upādhāva — you should worship
  Imperative of upa-√dhāv — run to. Same root that named the worshipers' running in v.4 and Vṛka's running in v.17. Nārada uses the precise verb for what asuras do at Śiva's door — fast, ardent, transactional.
• siddhyasi — you will succeed
  Present-as-future of √sidh. Material siddhi promised — but the chapter's whole point is that material siddhi from a swift lord is precarious. The warning is in the address, not the verb.
• alpābhyām — with even slight (qualities and faults)
  Dual instrumental of alpa (small). Śiva responds to small inputs with large outputs — pleased by a leaf, angered by a flicker. Mahā-deva's vātsalya is real, and exactly that vātsalya makes the system gameable.
• tuṣyati kupyati — becomes pleased / becomes angry
  Both present-indicatives in one breath. The same speed in both directions. The Gauḍīya reading: do not confuse the speed of mercy for the depth of judgment. Both come fast from giri-śa; deliberation rests with Acyuta.

• Have I ever received accurate advice that I used wrongly?
• Where does my use of true counsel determine whether truth blesses or backfires?

An archer tests two bows: one bends easily under any light pull, snapping to praise; the other holds firm and is hard to draw. Easy bows fly wild and snap fast. Nārada is telling Vṛka the technical truth — Śiva bends fast both ways — knowing the durmatiḥ will hear only the first half of the warning.