My Quant strats offer (professional hire)

I worked 3 years in a top IB as front office strats. Resigned July last year trying to go back to academia, however current lab is hard to generate papers, so I informed my previous bosses about my situation. They directly made an offer for me to go back. I have a couple of questions:

1. HR told me that the first year end bonus is not fixed. Is this normal? I thought professional hire always guarantees first year bonus?

2. It seems my year-end bonus will be pro-rated for this year, rather than paid in full. It looks to me a bit low-balled, is this normal?

3. HR didn't mention sign-on bonus. Is it a normal case for professional hire to at least have a sign-on bonus?

Thank you guys in advance !