Can I negotiate the commission rate?

Hello Ha, looks like you are asking as a buyer and wanting see if the agent will reduce their commission. If so, you will want to find out how the agent is getting compensated. Personally when representing a buyer I very rarely get compensated by the buyer at all. In general, the buyers agent will get a commission offered out by the sellers Broker. In this case, generally it is not standard practice to negotiate the commission if you are not the one paying it. If the buyers agent has an agreement with you on compensation then you can certainly ask if they would work with you on lowering their fee. Some are willing to do so, though others are not. Either way, in that case you can ask and unlikely going to be taken as rude.

Yes, but typically you may be different levels of service for varying commission rates. An agent should work for their commission so find out what they are doing for you.

You absolutely can. I would ask what difference in value they would bring at the two different rates(marketing costs/strategies, professional photo options etc)