Can I use my GI bill after using my voc rehab?

I am currently enrolled as a full-time student under chapter 31 vocational rehab. I was told that I can not use that in conjunction with chapter 30 GI bill benefits. Is that true? Secondly, after I graduate with a bachelors degree, my ch 31 benefits will stop (6 months after graduation). Can I then use my GI bill for a masters degree. I was told different things like it is a matter of time. That there is only 48 months of entitlement. My four year degree will put me at that, not allowing me to use the GI bill. Is that true? If I re-enlist in the military, will I be entitled to a new set of benefits? If it matters I was an 18-E in the Army with two trips to Iraq and a couple of other places. I did 7 1/2 years active and 1 year in the reserves and I am rated at 50% disabled. I spoke with a recruiter and I can go back in.