So when you said "without mods"... you still had Optifine? Please note that Optifine is a mod, and quite an invasive one.
Please refer to Optifine's changelog for compatibility information, as it is on the closed-source project to be compatible with the open-source one, not the other way around.
Hello! I want to figure out how to send a right click entity packet and to click a item in an container packet. For the right click I want to right click an NPC/EnitityPlayer and for the click a item in an inventory I want to be able to click an item in a certain slot of a container. Hope someone can help me out!