Does anyone have any experience with a child with extreme impatience?

My 4.5 year old cannot seem to grasp that things don’t happen instantly. For example, say he asks to go outside. I’m like, okay, let’s get dressed and get our shoes on. He immediately starts crying “why won’t you let me go outside right now?” I’m like, “because we have to get dressed. We have to get our shoes on.” And he cries and whines the entire time. If I’m cooking him something, like say he just wants some microwaved chicken nuggets, he will cry the whole time they’re cooking and ask “why won’t you give me my food? I’m hungry.” No matter how calmly I explain that they’re cooking, he doesn’t seem to grasp it, and just cries the whole time until they’re done. It’s like that with absolute everything. We cannot tell him any plans because he can’t understand why it can’t happen instantly. My parents are coming to spend Christmas with us and I can’t tell him because he will cry and whine and even scream and say things like “why isn’t it Christmas right now?” I don’t know how else to explain these things to him. I’ve shown him clocks, calendars, I’ve explained time to him, I have said “we have to wait for some things,” and he just responds with “I don’t want to wait.” What more can I do? Today he screamed the entire way home from the store because he couldn’t immediately have a popsicle I bought. I told him he could have one as soon as we got home, but he just screamed. So when we got home I said “sorry, you can’t have one because you decided to scream in the car and distract me. I told you how dangerous that is”. Now he’s just continuing to cry “why won’t you give me a popsicle?” It’s like he doesn’t get it. Truly. I figured at this age he would understand this a bit more? My 2 year old seems to grasp patience more.