Yes, you can do keto as a crash diet. But should you do it as just a crash diet? I’d suggest not. As I’ve said earlier, ketosis is a metabolic state of the body so it doesn’t make sense to get out of it, in say just three weeks.
Whoever says otherwise (looking at those self-appointed health gurus) is scamming you. The fight on whether carbs are good or bad has been an old one and always comes in the limelight, when someone tries to lose weight.
Keto isn’t one to differentiate between vegetarians and non-vegetarians. The only measure of difference will be in terms of the protein you consume. So instead of meat, your protein will come in the form of paneer and it’s fancy friend, tofu.