I read with 1 BTC deposit, I will be able to trade 100BTC worth of contracts.
100x leverage means your position will be force liquidated if the market moves < 1% against you. prepare to lose your 1 bitcoin!
Also, it is mentioned that there is no expiry for their contracts.
that's for perpetual swap contracts. they also offer traditional futures contracts.
Does it mean I will be able to hold if my position is even at losses? How exactly it works?
no matter what instrument you are trading, your position value must remain above your maintenance margin, otherwise you will be liquidated: