Shengei Visa is for the whole EU (escept U.K. and Ireland) , right ?

If I get U.K. Visa , can I go to Ireland with it? Or…

If I can’t , are they controling Passports at London-Dublin flights ?

I’m sure they do not control passports betwen Ireland and Northen Ireland

Note-I’m livin’ in SouthEast Europe , and for my country needs a Shenghei (and also U.K.) Visas …