You should ask what brand and where to buy as some look good but can be opened in just minutes. Some are light enough even loaded with 20 guns that they can be removed from your house with a hand truck. I have a Browning made in the 60's that the weight and thickness of the steel used is almost double what is used today and I can change the combination with out a lock smith.
Not if you bolt it to the floor, assuming there are holes in the bottom of the safe.