Can I be detained if I book a hotel online for 3 days and check out after staying for 2 days?

No, some international group hotels have special rooms, and the number of stay days is also required. If you can't reach a certain number of days, even if you don't live for enough days, you have to collect money according to the minimum number of days, but it's different at home. After all, it is a budget hotel, and the price is fixed, so if you leave early, just say hello to the front desk in advance, and it won't embarrass you.