It's not. There are certain obstacles to upgrading the CPU (socket type, BIOS compatibility, cost effectiveness, etc...), but there are no inherent disadvantages to upgrading.
Because it makes the CPU run hotter
Your motherboard may need to be changed when your CPU is upgraded.
You will need a new CPU,as well as the booting software
yes you can.
unlikely most laptops CPU are soldered to the board either get a new one or send it back for an upgrade
Most motherboards only support a specific subset of CPU's. If you change your CPU you MAY need to replace the motherboard... but if you do that it will include the appropriate BIOS. You may also need to re-install the Operating System.
In general laptops are not easy to upgrade. You MAY be able to add more RAM, but some laptops are sold with the maximum RAM they can handle already installed. You probably cannot upgrade the CPU, but you can't necessarily upgrade the CPU in a desktop without replacing the motherboard.The only upgrade that you can almost certainly make is to increase the size of the hard drive.
Upgrading a CPU is best left to a professional,you should be in a ststic free enviorment.
You can gain anywhere from 5-100% depending on how old your previous cpu was.
Depends on what you're doing. I'll assume you're doing some gaming, where in that case if the graphics card is pretty old, I would get a newer GTX 1060, which performs better than the 970 and is cheaper. But if the CPU is overheating, you may have to upgrade that ASAP. But a CPU upgrade will also require a new motherboard, [possibly] a CPU Cooler, and RAM.
yes, it used socket P
You have to figure that out for yourself.Some times people start out with an upgrade and really end up with a whole new computer.In most cases a CPU upgrade is going to increase your performance by around 5% at most.If that's worth the time and trouble to you then go for it.