Want to upgrade graphics card in lenovo c200 all in one pc?

You can't. Everything is integrated into the unit due to it's all in one feature much like a laptop. Only thing you can upgrade it the RAM and that would do anything for graphics or gaming.

Maintenance manual:
https://download.lenovo.com/UserFiles/UserGuide/en/User's%20guides%20and%20manuals/C200/Lenovo%20C200-HMM.pdf
No graphics card, and even if there were, it would be a custom card.
Graphics processing is either in the CPU or soldered to the motherboard.
An all-in-one is a lot like a laptop. If you want upgradable graphics, it is in Desktop/towers with a pcie x 16 slot on the motherboard, and hopefully also, a standard ATX size power supply.
With Intel Atom or NVidia Ion 2 processors, they are actually closer to a PDA or tablet than even a laptop.

Not upgradable.

Can i install a graphic card in lenovo c200 all in one pc

Can I change processor?

I have Lenovo c200. Display continues flickering what should I do?

Can I change processor?