My stab at it, anyway there are more than one way to express those questions.
1a-How much memory does this computer have?
1b-How much this computer has got? (Perhaps more used in British English, outside that it may be regarded "posh" - and both would be understood anyway.)
2-What is its (computer) processing capacity? Or what is the processor capacity?
(the seller will convince you in no time that it is the max, don´t ask that to a technician, because the answer is not so simple, ha ha ha.)
3-It has a built-in/internal WebCam, hasn´t it?
4-Which software it runs? (I preffer what Operational System it uses, because software is too broad a notion, you can use Java, CutePDF, antivirus programs, text processors - all are softwares)
Other (indirect) way: "is Windows or Ubuntu installed?" or still with the version "is Windows XP/7/8/10 or Ubuntu 10.14 (or 10.14 LTS, etc) installed?"
5-How long its battery lasts? (or ...lasts when it is unplugged without recharging?)
6-How big is the hard disk (HD) on this machine?