Does 20w apple adapter support iPad 10.5 inch pro

Yes - but you will need a USB-C to Lightning cable.

• USB-C to Lightning Cable (1m)

https://store.apple.com/uk/xc/product/MX0K2ZM/A

The 20W Power Adapter supports USB PD (Power Delivery) Fast Charging - as does your iPad. This Power Adapter will charge your iPad Pro 10.5” at its maximum supported 18W charging rate (i.e. 2.0A @9V / 1.5A @12V).

Yes. The 20W adaptor is a “good fit.”

Any Apple power adaptor - with the appropriate cable - will safely charge your iPad.

Although for iPads, the older 5W “icecubes” are generally inadequate for much more than either:

“Holding what you’ve got” … or “Slowing the rate of battery discharge”