CD4060 with external clock pulse
Can I give external clock directly to pin 11(RS) and leave pin 10(time
resistor) and 9(time capacitor) hanging without connection?

Yes you can but don't forget to connect MR (pin 12) to 0 volts.

Or can I give external pulse directly to pin 9 and leave pin 10 and 11
hanging?

Probably not.

will leaving other pins(11/10/9) hanging introduce errors due to
external noise as it is CMOS IC? I can't ground them though.

You should not leave pin 11 hanging. Pins 9 and 10 are outputs that happen to also connect to internal inputs.
I don't know what data sheet you used but this one says this: -