See my notes after your questions below:
1- What about other cordless phone which is higher then 900mhz. Because nowadays most of them is coming 2.4 or 3 ghz . Most will be spread spectrum and hop around. You won't be able to hear them very well for a long amount of time.
2- Can i listen cellphones? Just analog ones or digital also ? No digital for the most part. If you live out in the sticks someplace that has a cell tower close there may be a few analog phones left, but don't count on it.
3- Can i do Space and Satellite Monitoring? If i cant how can i monitor them? Yes and yes. For the best results an antenna with good gain will get you some of the birds, for the ISS you will only need a standard antenna and you will only hear them when you are in the "footprint" of their signal. Go to
www.amsat.com for more info on both.
4- What kind of things i can't listen from IC-R20 ? Trunking, encrypted, digital, and several freqs not available on the R20.
Can you recommed any better scanner which is portable ( I mean mobile like IC-R20 ) I dont want to buy the desktop ones. Again, as someone else asked, what is your main listening desire? There are MANY options out there and many are tailored to the listeners choice of monitoring.