i want to know if we should practice on the old Dlx part of the exam (before 2016) or only at the new Dlx part of the exam. in addition, i want to know if we should know JLAR (if i understood correctly, this commant mean call to a function).
You should practice all DLX questions from past exams. The question you will be given can be like the ones from before 2016 as well. Regarding JALR, it is not a complicated instruction and you should understand it. Its main use is indeed calling a function and then coming back to the place saved in R31 by the link part in JALR.