Cell phone upgrade programs?

I'm going to buy the iPhone but since is my firs time getting a plan i don't know much about upgrade programs. One of the main question i have is if i have to give my previews phone or do i get to keep it?

My iphone dropped in water. Will I lose the memory if i bring it in for them to fix

My iphone fell into a bucket of water and i put my phone in rice but when i turned it on it started glitching and i restart it and it won't let me type in my password. I saw a streak of water in it when i turn it to the side. This morning it seemed like the water was coming out a bit because it was different from yesterday. Should i leave it in rice for a few more days? I'm afraid of losing all my contacts and photos, (i don't know if i backed up the photos) will i lose them if i bring in my phone for them to clean it out? And what should i do about my phone?

IPhone 7 32GB or iPhone 6s 128GB? - 1

IPhone 7 32GB or iPhone 6s 128GB? - 2

Added (1). Suppose they cost the same price, which one should i get? Both value and storage are important to me so I really don't know which one to choose.