KA1: a solution containing hydrated ethanedioic(oxalic) acid, H2C2O4.2H2O, and sodium ethanedioate(oxalate).
As I supposed - hydrated doesn't mean anything here, as long as we are talking about number of moles. But you are asked to calculate mass of hydrated oxalic acid used to prepare the solution - thus you have to take mass of water into consideration as well.
How it is posible to prepare a solution containing sodium oxalate and hydrated oxalic acid with sodium oxalate itself?
Who told you it is possible?
Is sodium oxalate - solid?
yes
hydrated oxalic acid - solid?
yes
after adding water will become KA1?
KA1 can be prepared in several ways. You can weight some sodium oxalate, some oxalic acid (hydrated!) and dissolve them. But you can as well take oxalic acid solution (prepared with hydrated acid) and add some sodium hydroxide, or you can take sodium oxalate solution and add some hydrochloric acid - in the last case you will have solution containing oxalic acid, oxalate and some NaCl which is an inert salt in case of both titrations.
Am I right with my chemical equations?
Almost. C
2O
42- instead of C
2O
22- but it was probably a typo on your side.
Don't worry about hydrated part - it is important only when calculating mass of the solid. Solutions prepared with hydrated substance or anhydrous substance are in most cases identical.