How to open a bottle with old nail polish?

here you go https://www.wikihow.com/Open-Stuck-Nail-Polish

I used pliers.

Try pliers or kitchen shears. If this doesn't work, turn the bottle upside down, balanced or propped level, and drip nail polish remover in the crack between the lid and glass bottle; let this soak for a while, then try opening again. After it's open, clean the top of the bottle and the threads of the lid with a polish remover-damped cotton ball and a damp q-tip.

Sounds like the nail polish dried up under the cap. Holding the polish bottle upside down, drip some nail polish remover under the cap. Once the cap is off, be sure to clean out the cap thoroughly and rub all the threading clean with a rag dipped in nail polish remover. Good Luck :)