Pyotr's Uncle hasn't aged at all, even after a 10 year long period.
During the cemetery scene, when the rag union members, start jumping over random graves, it's extremely conspicuous, that the gravestones are just black carton boxes, placed on the ground for an authentic look, although it's been implied that they're on an actual cemetery; this was likely done to not offend those deceased people that were buried there. One carton box even features Eleanor Roosevelt's picture, glued on it.
When Popov causes an extremely damaging explosion to the house via a handcrafted bomb experiment failure, it's never explained how he himself didn't receive any damages whatsoever, considering the fact that he was standing in the closest range from it.