And, you ask about Plate Solving.....Yes, if you have the picture in the phone or pad, and you have an internet connection, you can do a plate solve.
But the term "Plate Solve" is often misused as a short hand for "Centering using Plate Solving."
"Plate solving" is only identifying the central coordinates (and perhaps rotation) of an image. It has nothing to do with moving the telescope to a desired point.
"Centering with Plate Solving" incorporates Plate solving into a routine that images, solves, moves, images, solves again, and keeps doing so until the rig is properly pointed.
If what you like about "plate solving" is that the software "plate solves" and then "Centers" using iterative plate solving and moving the scope, then you need to be able to control the telescope mount as well as Plate Solve.
I do not know of any phone/pad apps that can handle mount control. So, none (that I know of) can Center with Plate Solve.
I also do not know of any apps that can plate solve without an internet connection on a pad or phone.
But, if you have the picture in the pad or phone, you can use various plate solving services on the internet to solve the picture.
And, others may know of apps that do this stuff that I am unaware of.