Be sure not to focus on the weight limit only, that is more marketing than anything else. I personally had two children at the same time in a quality stroller claiming "up to 15kg" while they, together, were over 30 kg. On the other hand, small or cheaply made strollers can claim more but truly fit up to maybe 12 kg.
Truth be told, the Yoyo has a very short backrest, so even if possible to put a 4 years old in it, he or she won'' be comfortable much. The head right under the hood, falling behind as the 40-41cm backrest is too short to support it... and a very slanted seat making the kid slide down. So I personally would not pay so much for this buggy, it is a sturdy one, but not a roomy not comfortable one.
The Melio would be my choice here, however it is also on the weaker side. As a reversible stroller, really found on maybe 2.5 - 3 years of age, it doesn't really matter how many kilograms. But if you want a sturdy one, rather go for the Cybex Mios, a similar model but a much higher quality one. Melio, and Mios are also much more comfortable for a newborn baby, so definitely don't go for an ultra-compact stroller like the Yoyo if wanting a good pram for your little one from birth.
Hope I helped ^-^