I am new to this whole thing about antminer.
This is my screenshoot of my antminer A3. It is still safe that the chip temps reach up to 90 C?
Also what software can we use to monitor our A3 from outside computer ?

90 is a bit high, you may want to manually set your fan. Start at 95% and lower until you feel comfortable (also note that these machines are buggy and sometimes a simple power cycle will have it running a little cooler).
I have mine running in a cold (50-55F) basement with the fan set to 90 and the clock set to 631 and the hottest chips are running just under 80C. Which is still slightly uncomfortable for me, but since it ran stock at 84C so I'm cool with it. 90 is worrying, though, and I'd try upping your fan speed.