Can I get benefit of theta or benefit of time decay on holidays if I am a option seller?
you can… but price of option won’t change on holidays… the price will automatically factor in the holidays and according to that theta decay will play out…
After holidays when market will open then will I get the benefit of time decay?
Technically Yes. but also it all depends on the market volatility. If market Gap-Up or Gap-Down, You might see option premium going up also due to high volatility.
To Benchmark volatility India VIX is the parameter.
Holidays will be factored in option price even before the holidays.
You might see significant decay in second half of Friday.
Theta and time decay is none or the less the same, if thats what your question is about.
Selling option has unlimited risk and little gains. Unless you are an institute with a ton of money or an experienced professional who knows what he is doing, never sell naked options.