@akriti, when page tables are first loaded than that hsould be in kernal mode as Dispacther is responsible for loading a p/c with its content and Dispatcher is called by Kernal mode to execute as far as i know. when talking about modification in page table than a p/c while executing itself can modify it's table. so there should not be Kernal mode in this. Not sure about point 2 though.
2nd ques.. that page table are stored in PCB. nope whole page table is not stored in PCb.there is Memory management information in PCB : includes the information of page table, memory limits, Segment table depending on memory used by the operating system.
for 2nd ques. of yours , source is wikipidia. https://en.wikipedia.org/wiki/Process_control_block