A: Yes, depending on your rank. All company grade officers carried a smaller musket called a fusil on active service when outranked by a more senior officer.  For example, Lieutenants (Capitaine en Secondes) and Captain (Capitaines) carried a fusil when outranked by a senior Officer (Major or Colonel). Ensigns however, even when not bearing colors would not carry a fusil.

All Company grade officers carried fusils while under arms at a position we call "advance". There is an entire section of the '79 regs that are dedicated to this drill. When the officer steps away to post, the Sergeant steps up, brings his musket to the advance and takes charge.

The fusil is exactly the same as the men's muskets with the exception that the barrel is 4 inches shorter and about 3 pounds lighter and like all smoothbore arms in the French army at this time, it is a .69 caliber musket. The weight was reduced by having a shorter and lighter barrel and as such, the stock would be lighter to support the lighter barrel and slightly smaller lock.

For company grade officers, the cartridge box is smaller and carries only 18 rounds.