Can i use my iphone apps on a ipad?

I have iphone but would like ipad and if i have apps on my Iphone but i say changed to a different phone would i be able to log into the ipad with the same log in details as i use on the iphone and get the same apps, also would they be at the same place like on Simpson's tapped out i'm on level 31 so would it start from that level on the ipad or would i be taken back to level one cos its a new device?

All iphone apps should run fine on ipad also. (Just that those written for the ipad specifically make sure of the big screen).

As long as you sign in to the same game center then yes.