No it can,t. roar of time is dialga's signature move and spacial rend is palkia's signature move, and only those Pokemon can learn the corresponding moves. By cheating and hacking of course you can...
Level 40.
Palkia learns Spacial Rend at level 40.
You can't, unless you use an action replay. They already ended the event that gives out the one that you want.
Arceus cannot learn roar of time or spacial rend.