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Equal payment: the same amount (principal + interest) every month. Equal principal: the same principal every month plus interest on the remaining balance, so payments start high and decrease. Bullet: interest only every month, with the whole principal repaid in the last month.

With monthly rate r = annual rate ÷ 12 and n months, the equal payment is loan × r × (1+r)ⁿ ÷ ((1+r)ⁿ − 1). Each month the interest is the remaining balance × r, and the rest of the payment reduces the principal.

Months in which you pay only interest. The principal is then repaid over the remaining months, so monthly payments and total interest go up.

Yes, slightly — banks may round differently, charge daily interest, change rates or add fees. Amounts here are rounded to the nearest won, and the last month settles the remaining principal.