i5 yes; i7, no.
The system had the option of an i5-2410m, so that CPU should work. So should others in the same family.
If you're still running a conventional hard drive, a solid state drive is a far more cost-effective upgrade than any CPU upgrade you can use.
upgrading i7 is completely impossible or one should consider other factor such as cache memory RAM etc....! what are other things that should also be upgraded?
The system won't take an i7 - the mainboard isn't designed for one. Just about anything other than an SSD or RAM upgrade is either impossible with this system, or just not worth the effort and cost. It's an outdated budget system that just isn't capable of certain tasks -- no upgrade will change that.