Does ALS affect speech?

Yes it can. ALS causes tongue atrophy, which can lead to articulation challenges and "dysarthria".
Yes. Speech will be affected and over time a person can lose the ability to talk. This is due to progressive weakness of the muscles we use for speech.
Yes. Eventually the muscles used to form speech are affected, and the patient becomes unable to speak. There are many adaptive devices available to help persons with ALS communicate.