Hi, i just achieved First Officer Rank, i was just wondering though, is it possible to fly Class 1,2 and 3 Planes or is it 2 & 3 only like it says in the handbook? if 2&3 only, why not class 1?

I did not write the handbook, so I may be corrected on this subject. What I can interpret this is, as you gather time and experience you never lose your rating i.e. class 1 aircraft so as a First officer you can operate class 1,2 and 3 routes and aircraft.
By the way congrats on your efforts.

I didn't write it either but just have continued to update it over time

Yes - what Frank has indicated here is correct. Once you have achieved that rating you do not lose it.

Cheers!