share based payments questions

Hello Mike i have questions to ask on share based payments 1. lets say we have share options and vesting period is 2 years and at the end of 2 years the total liability is 500 and expense was 250 each year in Pnl. now what if employees decide not to exercise their options for any reason. what do we do with the liability of 500 and expenses in pnl of 250 each year? 2. is my understanding correct that IFRS 2 covers buying of goods and services only except derivative contracts, treasury shares and rights issues etc. it also does NOT cover the situation where a company issue shares to buy another company because that is covered by IFRS 3 business combinations? please correct me if i am wrong here. 3. when do we use intrinsic value in share based payments? is it only when we pay for the shares?