How many number of confirmations before a Monero can be spent? Also, if there are two or more users opening the same wallet connected to a different node would a user connected to a faster node has an advantage of having earlier confirmations?
Newly received coins can be spent after 10 confirmations.
I case two conflicting transactions are sent to the network by two clients managing the same wallet, the first to arrive at the node that will mine the next block will probably be considered as the valid one, and the other transaction will then be rejected.
Being connected to a faster node with faster connections to the other nodes will help broadcasting a transaction faster, but if the slower node happens to be connected directly to the node that mines the next block, its transaction will probably be confirmed and the faster node's transaction rejected.