"I buy 100 RFMD at $28 on 10/01/2000, another 100 at $25 on 10/15/2000 and finally sell all 200 at $20 on 11/05/2000.

Am I allowed to take the losses (100x8 + 100x5) against my income?"

Reading ahead, yes.

"ie are these sales cleared under the wash sale rule? Note that even though I made a trade within 30 days prior to the sale, I am selling all my positions on 11/05/2000 and staying out of it till atleast 12/06/2000."

That's the important point. You are allowed to sell
at any point after buying. It doesn't matter whether you had bought the stock once or twenty times. What
makes a wash sale is buying back within 31 days of selling. Now, if you had only sold 100 shares, once
can say it was a wash sale because you bought 100 within 30 days of the sale. That is, on 10/15 you set up to have 100 left after selling 100. But that isn't what you did. You sold out of the stock. Now, as long as you STAY out for 31 days, you can take all your losses.

"Also, what happens if I now buy back into RFMD on 12/20/2000? This question might be moot depending on the answer to the previous question"

Then you own the stock again, but more than 31 days elapsed since you last owned it. No wash.
Shame. I made a bunch of money on that stock last year....sold in February. Best wishes, Chris