- Should Arceus be part of the psychic type list as it can be a psychic type?
No. it is the creator, and therefore he must be neutral, and what will the mind plate serve if he is already part psychic. Normal fits him perfectly, and if he is ever made a psychic type, arceus would lose part of his usability, barring mind plate as just a move booster, instead of the godly ability to change Arceus' type.
- Do you think that Psycho Boost, the most powerful psychic type move, should be learnt by other psychic types other than Deoxys? Why or why not?
I have never heard of Psycho boost, but if it is the strongest one, I am in complete disagreement of having the other types learn it. There is a reason why deoxys is the only one that could learn it. If ever the other Pokemon could learn it, Psycho Boost would just be another, albeit a strong one Psychic type attack.