Assuming that you have unexercised options granted at €4,700 for shares that are now worth €8,600 then if you exercise and sell you will be liable for income tax of 42% on €8,600 - €4,700. Not sure of you are also liable for PRSI (4%) and/or health levy (2%).
I'm afraid not. The figure you mention is the capital gains allowance and this is taxed as income (the company are effectively giving you difference between the exercise price and the market price). If you exercise and hold the shares, then any further gains on the €8,600 would be taxed as capital gains (at 20%) the first €1,270 of which in any given year is tax free.