future project assistance needed

Good afternoon I am new to the community and just joined a few moments ago. I have a few questions regarding raspberry pi projects and I hope to receive some assistance. I currently do not own any raspberry pi products but for the project, I am looking to work on I will need some assistance on product selection, compatibility, and Electrical technical support the current questions I have are as follows 1) I am unsure of which raspberry I should purchase because I am new to this whole thing. The project in mind would be setting up a row of buttons which once pressed tells the program to play a specific video so my question for the first one would be which raspberry computer would be best suited for playing different videos when a corresponding button is pushed 2) my second question is on compatibility. I know there are buttons that are sold either with a computer or separately, but I noticed the raspberry computer has USB ports. Would I for example, be able to use a stream deck to run the videos once the corresponding button linked to the video has been pushed. 3) my third question is relating to power supply and technical assistance. What is the power supply needed to run such a device? Would I be able to plug it straight into a wall or a power source that is always live so it will run all the time unless I click the power switch, or when power is added to the system 4) how big of a screen can the raspberry systems control if that is the correct word I should use basically how big of a screen can be used 5) also would I be able to store the files and the code on a USB or a SD card and be able to run the programs from there? For example if I wanted to add more videos or change the videos, would I be able to take a USB or SD card with the files on that and then plug it into the raspberry computer and push a button and it will play the video that is set up for that button if that makes sense

I am new to this whole raspberry computer and have absolutely no experience with any such products, but I am looking to make a project where a small computer would be necessary. Any help would be really appreciated. I also apologize if I did not set this post up to a specific format and I await your answers. Apologies again and thank you.

1) I don't know what kind of budget concerns you have. Are you trying to optimise the cost so you can scale it? I think for what you describe, a Pi 4 at least is probably ideal. If money is not a concern, you could just as well get the Pi 5 and get the best performance. 3) AC-adapters are available and is sold separately. Its specs will depend on the model. 4) The Pi 4 and 5 support up to 4K displays. However, I have only seen them run up to full-HD video smoothly. 5) The Pi boots from an SD-card by default. You can plug in additional storage via USB. I don't know if it supports auto-play out of the box, but you can probably find a solution for it. In essence, main series Raspberry Pi are low-cost single chip computers built with the ARM architecture which are also used in smartphones. Size that of a credit card. Performance in the latest Pi 5 is about half that of a mid-range i7 PC from 10 years ago, which is really impressive at such a low cost and tiny format! There are also microcontrollers and stripped down Pis for much lower cost and energy usage which are suitable for lighter tasks.

Apologies for using the wrong word as I mentioned above when I am referring to play videos I am talking about little clips. Probably a minute is the max length but if the clips are shorter, they would probably be set on loop.