I currently attend UCSB and I am planning to go back home in the spring to attend a cc. I looked into the TAG program and have a few questions (hopefully some of you guys know the answer to):
make an appt with an admission counselor at ucsb to get answers since they should be quite familiar with the TAG program. Don’t be worried that they’ll be upset with you for wanting to leave ucsb; in my experience counselors really want to help students get what they want, and if its a college somewhere else they’ll do their best to help you get it done. Note that you are not eligible to use TAG for ucsb.
There is no “reset” on gpa. They use xferable courses from all prior colleges attended. Furthermore at your new UC the overall GPA they calculate will still use the UCSB units; UC grades are with you forever at UCs 
See the UC TAG matrix http://admission.universityofcalifornia.edu/counselors/files/tag-matrix.pdf for requirements to submit & complete TAG, also talk the the ucsb counselor about the rules. Rolling the years forward by 1, Davis would require full-time enrollment at a CC from spring 2015 on to file. None of the others have this clause. But the part you need to ask the counselor is about this
It isn’t clear if you need to meet this definition at 1) the time you file the TAG 2) the end of your studies at a CC. After all you can be “considered” based on something you plan to complete, in the same way they require 60 units to xfer but you apply before you’ve actually completed those 60 units. If it is (1) then you can’t apply for Fall 2016, if it is (2) you can. I don’t know the answer, and if you find out from a UC counselor please post the answer so we’ll know in the future.
There is no time limit on when you need to complete the TAG requirements, so far as I know; many CC kids take 3 years. Be careful about “take your time with it” since there are unit caps for xfers and all of your UC units count towards it. I’m not going to pretend to be an expert on this, but talk to someone who is to make sure you don’t inadvertently make yourself ineligible to xfer.
Just to be clear, you mean that you want to attend a community college and then apply to transfer to a different UC campus? You cannot use TAG to return to UCSB if you already go there. If you are planning to transfer to a different UC, your GPA from UCSB will go with you. For the TAG program, I believe they will average your GPAs from UCSB and CC together. If you are admitted to a UC though, then you will enter with only your UC GPA (not including the CC GPA), so you generally have to be at least in good academic standing when you leave UCSB.
I believe that a student cannot be admitted to another UC if they are in bad standing at a previous UC