The isolated whitish patch on the plastron of your tortoise is some light scoring (=scaring) most likely from sitting in urine when it was a new hatchling. This commonly occurs when several neonates are housed together and as a result they quickly soil the substrate they're kept on. As their plastrons are still rather soft and not completely hardened off, they are susceptible to getting 'burned' from the acidic urine or bacteria in their substrate.
You will notice that this patch is on the oldest part of the plastron that corresponds to its neonatal portion of the shell. All of the new growth that the little guy has put down is perfectly healthy and normal looking.
As this is scar tissue it will not spread or get worse and in fact, by the time the tortoise becomes a young adult this will likely have worn away and if not, will just be a tiny blip you won't notice.
Save your money on a vet visit! You can smear some cheap anti fungal cream on the spot if you want to insure that there is nothing active taking place...but I doubt that you have anything to worry about.
As for the raised area on the carapace it too doesn't worry me. Tortoises raised indoors almost always have at least a little bit of pyramiding or at least slightly sculpted shells. Not always, but usually.
You will get tons of theories and countless opinions on this topic but my advice is to provided a humid hide (that you keep clean), avoid direct lighting by heat lamps that quickly dry the shell, and then moderate the food intake. Avoid the high sugar commercial diets (= Mazuri, and the like) except as occasional variations in the diet and make sure the tortoise stays hydrated.
Grow your tortoise slowly and well. He or she will be fine.
Growing slowly does sound weird...ok, what I should have said was do not 'push' his growth. In other words don't offer huge amounts of food every day, especially the prepared commercial diets. Don't feel that you must have food in front of the tortoise every day--it's ok to skip a day once or twice a week and especially as he or she gets larger.