No. Keys are platform‑specific. Console versions embed the license in the digital download or disc; a PC key will be rejected.
Never. They typically distribute pirated or already‑used keys, which can lead to malware infection or instant bans from Rockstar services.
Contact the retailer for a replacement receipt. If the retailer can’t help, you may need to purchase a new copy; Rockstar does not re‑issue keys without proof of purchase.