Can I Give Delta Gardevoir A Dawn Stone?

I wanted a strong physical attacker. Is there any way to change their evolution? If not, where can I get Delta Ditto for breeding?

you cannot change the evo branch of a pokemon once it has evolved. The earliest (and only) time you can get a Delta Ditto in game is postgame in Metchi Town after meeting the conditions necessary (check the wiki for more details). If you do really want a d. gallade, you can ask for one in the trades section. In my personal opinion, something like d. scyther would be a better physical attacker, as d. gallade’s moveset (especially its STAB moves) isn’t as consistent and powerful as d. gardevoire’s.

thank you my friend

no prob, good luck with your playthrough :))