Hello Ioac
No, you cannot use the same public IP address for two different private IP addresses in this manner. The NAT process is designed to map each private IP to a unique public IP. This is necessary to correctly route return packets to the appropriate private IP. If you were to issue the two commands in your post, the second command would overwrite the first.
The extendable keyword allows the router to map a single private address to multiple public addresses, and not the other way around.
However, if you want to map multiple private addresses to a single public address, then you would use the “overload” feature of NAT, which is essentially PAT. For more information about PAT take a look at this lesson:
I hope this has been helpful!
Laz