Yes, after a year solids become the primary source of nutrition, although most babies will start to transition to taking more solids after 9mos. It is more of a gradual transition rather than a large change, and you will see as your baby grows what works best for them.
Some baby food does tend to get a little water upon defrosting. I don't think the taste changes so much. If you like, when you make it don't blend it up too thin. Then once it's defrosted you can decide whether or not to thin it out a bit. Personally I never had any issues with freezing and defrosting foods, and when I did purees with DS1 we moved past the thin, watery stage really quickly and the thicker purees held up fine when frozen and defrosted.
I think it's a good practice to put baby in his chair for every meal. It's also better from a safety point of view that they are seated upright in a proper chair.
Good luck! Please feel free to start your own thread if you have more questions, of course we are happy to help you through this stage (I remember having lots of questions when I first started out with DS1).
