The A1 licence is aimed at 16 year olds to allow them get on the road. Over 18s can apply for an A licence. Also if you have a car (B) licence, you are licenced to drive a bike of up to 50cc and not capable of more than 45 kph. That is a B licence also grants you licence to cover category M and also W (work vehicles)
The power restriction contrinues for 2 years after you get your full licence. So if you do not apply for your licence immediately after passing the test, the restricted period will be more than 2 years.
That's unless the government introduce Direct Access as they are required by EU law to do... 2 chances of that then. Direct Access allows a rider to quality on bikes without power restrictions.
One bit of advice I would give. Apply for the test ASAP. The waiting list is waaaay too long. Also get some lessons, see other threads
Star Rider courses run by Fingal Co Council are off the road until mid-Feb. So your only option at the moment is to get a bike, get IRTA lessons. The lessons will not only help to pass the test, but improve your chances on the roads. It is _not_ easy, but it is satisfying to get out on 2 wheels.