Can a shampoo containing beer can remove dandruff from oily scalp? Is there any side effects? Will it decrease hairfall?

Doubt it seriously. I know of no logical reason that beer would decrease dandruff - and you'll smell like a brewery besides. You'll find many effective anti-dandruff shampoos in any drug store; if those don't work a dermatologist can prescribe a stronger prescription shampoo. As for hair shedding, you normally shed 60-100 hairs per day, all of which will grow back. If you're losing more than that, see a dermatologist.