how anyone can find out that the stock is trading at the lower circuit or tomorrow the stock is going to hit upper circuit.

what is the circuit fundamentals and how do they assist in knowing the trading signals if any are generated from them?

You can check the upper and lower circuit limits on the market depth window of a particular security on Kite.

Circuit limits are determined by the exchanges to curb excessive volatility and speculation. Whenever a stock hits a circuit limit trading in that scrip is stopped. Circuit limits on NSE/BSE range between 2%, 5%, 10% and 20%. The exception to these limits are stocks that trade in F&O in which case no circuit limits are applicable.

For ex, if Nifty moves by 10% then trading is halted for 45 mins if it moves by 15% trading will be stopped for 1 hour 45 mins and if it moves by 20% then trading will be halted for the entire day.

or tomorrow the stock is going to hit upper circuit.

I’ll let the more qualified members comment on this.

where can we get the full list of stocks trading at lower price band ?

if i buy tomorow the halted stocks, then can it gain the momentum and go up or it will remain in the dull mode only?

That depends on your analysis.