Whole30!

So, I'm going to give whole30 a try - and I have a few questions.
First of all, I am not doing it because I want to continue with it my whole life, but to challenge myself and to boost my weightloss a little bit.
Now, what I wanted to know is;
1. If you drink that long no milk and consume no dairy products, isn't there a chance to become lactose-intolerant? ( For sure nothing I would like to risk )
2. Did you experience a yoyo-effect? After 30 days of not consuming bread, pasta, rice, dairy etc. and then starting slowly to consume them again, isn't there a possibility of gaining weight back? - Even if you stay within your calorie deficit.
3. Generally, what are your experiences with whole30? Yay or ney?
Thanks in advance!
Sarah