JSYK, item #3 upload is not possible in Adalo today. Item #3 download requires a customer components which I do not think exists. Item #2 is not overly simple with the current state of Adalo. You can use the component build by @knight on his store (I think it was Knight with the countdown timer), but even that, the user needs to be in in part of the app that runs the timer, or the timer needs to be on every page.
Item #1 sounds simple enough to tackle.
Not bidding on the project, just metering expectations for you and whichever expert comes along.
Please note that for number 3 it is not possible but what i can do is that the user select one photo upload it and then it come to a bottom side of the screen and the user can keep selecting photo and photo until they are and done and upload it