I've neglected this bike, a Marin Bridgeway, for the past 3-ish years. It's spent a significant part of that time sitting in the sun and (occasionally) rain. I want to fix it up again, but I have no knowledge of bike maintenance and want to just run things by someone more knowledgeable than me to set me on the right track. The main problems I can see that would affect useability are that the tires are flat, and the chain is pretty rusty and has slipped off the chain ring. The back cassettes also look pretty rusty. From the small testing I've done, the wheels seem to turn fine, and when I squeeze the brakes they seem to work, but it's hard to know without riding the bike. I can't really tell whether there are any problems with the shifters at the moment.
For the tires - I see tiny cracks all along the side of the tires. I photographed the worst ones on the front and back tire, respectively. Is this a sign that I need to replace the tires entirely or is this okay? I am also thinking that I'll probably need to replace both of the inner tubes, since I recall that one of the reasons I stopped using this bike was I kept getting a flat tire, but I don't actually know how to check the quality of the inner tube.
For the chain - I looked at some online tutorials and think I can remove it myself. After that, I'm not sure how to tell whether the chain is in good enough condition to just remove the rust and put it back on, or whether I need a new chain entirely. This bike forum post recommended using Evapo-Rust to remove the rust.
For the cassette - I also want to clean the rust off of it, but I'm a bit less certain on how to remove the cassette from the bike. Do I need specialized tools to do it? What is a chain whip and what is its purpose? I don't own any bike tools at all, so to keep down expenses I'd like to minimize unnecessary purchases.
In addition to making it rideable, I would also like to fix up the appearance of the bike a bit. My dad gave me this bike as a gift and I feel bad for having let its condition deteriorate. In particular, most of the screws and bolts on the bike look fairly rusty too, and the top of the seat looks a little worn. My idea is to remove the screws in small batches, cleaning them with a rust cleaner, and reattach them.
Thank you so much to anyone who takes the time to offer my guidance and advice. I am very grateful for your help and look forward to understanding my bike better!