Roots came outside the pot. Should I transplant it?

There is no real danger, the roots that come out of the holes will "self prune" once in the light and air. However, it does indicate your plant is not far from being "root bound" as the roots are already looking for more grow space. You can leave it in its pot, but it would probably be best to switch to flowering soon, before it becomes a real problem. Transplanting would be sensible if you are keen on keeping it in veg for a while longer. Transplanting would also ensure that the plant will be able to grow much bigger, and naturally this translates into a much larger yield. A 40-50 litre pot would show much greater size and yield. A plant can only grow as big as the root system can support it. Basically, more roots = more plant. Remember too, to fill your pots right up to the top, this maximizes content of your chosen pot and provides the most room for future root growth. I am constantly dumbfounded by people who want to grow the biggest plants possible, then only filling their pots to 50-65% capacity, severely limiting growth potential. If you do transplant, give your plant 2-3 weeks at a minimum to get settled again, before any moves to a flowering cycle. I would also suggest stopping any further leaf removal, - more leaves = more energy produced = larger and faster growth. Nice job with the training though! Hope this helps,........... Organoman.