question: the category which he will be competing is ornamental/celtic.
Capitalize this past sentence correctly.
A: The category which he will be competing is Ornamental/Celtic.

question: unsure about which type of j2s file you have? do you want to know exactly what it is, who created it, and how to open it?
Capitalize this past sentence correctly.
A: Unsure about which type of J2S file you have? Do you want to know exactly what it is, who created it, and how to open it?

question: at first glance, the tokyo apartments designed by sou fujimoto look like one of those pictures by m.c. escher.
Capitalize this past sentence correctly.
A: At first glance, the Tokyo Apartments designed by Sou Fujimoto look like one of those pictures by M.C. Escher.