If I put a number in a new iPad Apple ID will it share my messages photos etc.?

I bought an iPad for my sister and created a new Apple ID as she never had an Apple product before. It asked for a number, which she does not have, so I put mine. My question is will it share all my data? Will she able to see my messages in iMessage? Will she see my photos or anything else that’s on my phone? I also wonder if it’s possible to remove my phone number from that Apple ID without any problems, and if putting my phone number for that iPad will create issues for my Apple ID and make me lose anything.

I also have another question. I purchased the iPad with just WiFi, not WiFi + cellular. Is it possible to double check through the settings if I received the correct one?