We can't really answer that until we know WHICH 45 and which 50. In the case of a muzzleloading black powder rifle, the .50 with have more energy, all other things being equal. However, it could also compare a 50 muzzleloader to a .45-70 cartridge rifle, which is more powerful. Caliber alone only tells us the width of the bullet.
yes
It depends on the load
The .45 caliber bullet is not used in a sniper rifle.
trade it in for a 45 caliber
Yes
Depends on the load
Depends on which 45 and which 44 chambering you are talking about the load
100-400 USD
Shiloh Sharps caliber 45-110. Nice rifle, huh?
Impossible to answer without the sn and maker.
No. the AK-47 assault rifle is chambered for the 7.62x39mm round, which is equal to the .30 caliber. The .45 caliber is simply too large for the AK-47's bore, not to mention it is a pistol cartridge, which has a completely different design than a rifle cartridge.
45-80 dollars,depending on the overall condition of your rifle.