Um, you basically can't. Most laptops are not designed to have parts swapped in them. Typically limited to memory and storage upgrades only. Some laptops have socketed CPUs and GPUs, but usually only higher end hardware.
I'm not sure that is the proper model for your laptop. That might be a sub model, but it should have a name like Pavilion.
Not sure what you mean by ROM. The only ROM inside of a computer these days will be the BIOS itself. Optical drive is a type of ROM, but there are also writable discs, so it doesn't really apply. Also removeable.
No idea what you are talking about with Intel HD. Those graphics are integrated to the CPU, so if it is socketed there is a small chance of an upgrade, if not, the best way to get more graphics performance is to replace the system. If it were new enough, you might consider an external GPU, but I'm guessing this isn't a model that can support that.