Round 1 :
Design LRU cache

Round 2 :
Check if a tree has all it's left node smaller than right node

Round 3 :
Unique Path 2 (Basic dp problem)
Design Tic-Tac-Toe

Round 4 (Hiring Manager Round):
Find right sibling and left sibling of all nodes , parent node provided in O(1) space , suggested bfs but that needed O(n) space , came up with a solution but could not implement it properly.

Three tapes T1,T2 and T3 . Add T1 and T2 , store the last digit of the sum in T3 and forward the carry to the previous node . Once you move ahead in the node , you cannot come back to this node. Way too many nodes to store in any DS . After asking he allowed to use stack for limited cases . Could not come up with a good approach.