need help for general question about wallet,.

I have plan to copy and backup my wallet (same multiple wallets) to a several PC's (devices)

what will happened if I copy my wallet (multiple wallets) to several PCs ?, it is safe and allowed,.
the wallet definition in crypto coin make me confused,.  what will happened with all addresses in that wallets,
is that mean all addresses in that multiplied wallets will same (an address will be in all the wallets, how about the coin itself),.
and how about sync, if all of that wallets app run on all the PC s at the same time.

Thanks in advance for the help and guidance